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HISTORICAL RESEARCH REPORTResearch Report TM/88/18

1989

Hearing abilities of a group of mineworkers in relation to their age and estimated noise exposures Final report Robertson A, Howie RM, Maclaren WM, Dodgson J, Garland RP, Afacan AS, Jones K, Wood N, Bellamy M, Fisher P

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Hearing abilities of a group of mineworkers in relation to their age and estimated noise exposures Final

report

Robertson A, Howie RM, Maclaren WM, Dodgson J, Garland RP, Afacan AS, Jones K, Wood N, Bellamy M, Fisher P

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HISTORICAL RESEARCH REPORTResearch Report TM/88/18

1989

ii Research Report TM/88/18

Report No. TM/88/18UCD 613.644:622

HEARING ABILITIESOF A GROUP OFMINEWORKERS INRELATION TO THEIRAGE AND ESTIMATEDNOISE EXPOSURES

A RobertsonRM HowieWM MaclarenJ DodgsonRP GarlandAS AfacanK JonesN WoodM BellamyP Fisher

January 1989

Price: Price:£40.00 (UK)

: £45.00 (Overseas)

Report No. TM/88/18

INSTITUTE OF OCCUPATIONAL MEDICINE

HEARING ABILITIES OF A GROUP OF MINEWORKERS INRELATION TO THEIR AGE AND ESTIMATED NOISE EXPOSURES

by

A Robertson, RM Howie, WM Maclaren, J Dodgson, RP Garland,AS Afacan1, K Jones2, N Wood2, M Bellamy2, P Fisher1

FINAL REPORT

1 British Coal Corporation Medical Services

2 British Coal Corporation Scientific Control

Institute of Occupational Medicine8 Roxburgh PlaceEDINBURGHEH8 9SU

Tel: 031 667 5131Telex: 9312100237 =TD G January 1989

This report is one of a series of Technical Memoranda (TM) published by theInstitute of Occupational Medicine. Current and earlier lists of these reports, andof other Institute publications, are available from the Librarian/Information Officerat the address overleaf.

For further information about the Institute's facilities for research,service/consultancy and teaching please contact the Librarian/Information Officer inthe first instance.

CONTENTS

Page No.

SUMMARY 1

1. INTRODUCTION 3

2. PRELIMINARY INVESTIGATIONS OF THE RELATIONSHIPSBETWEEN MEASURED AND ESTIMATED NOISE EXPOSURE 5

3. METHODS 7

3.1 Noise measurements available for study 7

3.2 Formation of Noise Occupational Groups 7and Assignment of sound Pressure Levels (Leq)

3.3 Calculation of Noise Exposures 8

3.4 Audiometry 9

3.5 Statistical Methods 10

4. RESULTS 13

4.1 Noise Levels and Exposures 13

4.2 Hearing Levels of Mineworkers at Colliery Q 13

4.3 Hearing Levels by Age and Noise Exposure 15

4.4 Hearing Performance of Left and Right Ears 15

5. DISCUSSION 17

6. CONCLUSIONS 21

ACKNOWLEDGEMENTS 23

REFERENCES 25

TABLES 27

FIGURES 41

APPENDICES

INSTITUTE OF OCCUPATIONAL MEDICINE

HEARING ABILITIES OF A GROUP OF MINEWORKERS IN RELATION TOTHEIR AGE AND ESTIMATED NOISE EXPOSURES

by

A Robertson, RM Howie, WM Maclaren, J Dodgson, RP Garland,AS Afacan, K Jones, N Wood, M Bellamy, P Fisher

SUMMARY

Using existing noise level measurements, detailed working records of individualminers and data on hearing abilities supplied by British Coal Medical Services, thehearing abilities of colliery Q coalmine workers have been investigated in relationto their age and noise exposure.

Noise levels in colliery Q were typical of those found in the British Coal Industry.The individual mean lifetime exposures (average Leq) to noise were found to liebetween 86 and 93 dB(A) with 83% of men exposed on average between 88 and91 dB(A). The hearing levels of the colliery Q miners were, however, found tobe similar to predicted from typical age-matched, non-noise exposed populations.These differences are not readily explicable from the data available and requirefurther investigation. There was no significant correlation, after allowing for age,of hearing level with noise exposure amongst a subset of 197 men whose estimatedlifetime noise exposure was well defined. In view of the forthcoming noisecontrol regulations and the fact that we do not know whether colliery hearinglevels of Q men are fully representative of the UK coal industry we recommendthat a further cross-sectional study is undertaken to investigate hearing levelsamongst miners from a number of collieries in relation to age.

1. INTRODUCTION

The relationship between hearing ability, age and occupational noise exposure hasbeen studied in detail (BAUGHN, 1973; ISO, 1974; ISO, 1985; BURNS andROBINSON, 1970) and this work has been used as a basis for legislation tocontrol occupational noise exposure. Current and proposed UK legislation restrictspersonal exposures to equivalent continuous sound levels (Leq) of 90 dB(A) over aneight hour working shift (FACTORIES, 1974; HSC, 1987). Noise exposure levelsin the British coal industry have been found to be around that level during mostwork activities (JONES, 1986; LANCASTER, 1986; JONES, 1988) but limitedstudies of hearing loss amongst selected mineworkers have revealed that hearing lossat low frequencies and social disability were considerably less than expected fromsuch noise exposures (DICK, 1975; DICK and COLEMAN, BRITISH COALINTERNAL REPORT 1979). It was therefore considered that an epidemiologicalstudy of noise exposure and hearing loss in the coal industry should be carried outto ascertain whether the effects of age and noise exposure on the hearing abilitiesof mineworkers were consistent with those predicted from the data upon whichcurrent legislation is based.

There are, however, difficulties in carrying out such a study, particularly associatedwith the measurement of personal noise exposure levels and the calculation of longterm noise exposures. LANCASTER (1986) and McCORMICK (1987) described adetailed study of personal noise exposures using dosemeters at three collieries overa period of six months starting in 1983. There were two main conclusionsregarding noise exposure measurement strategy:

(1) Direct measurement of individual coalminers1 long term exposure to noiseis impracticable if reasonable accuracy is to be achieved;(2) Noise exposures can be calculated from static sound pressure levelmeasurements in favourable circumstances but the amount of detailed informationrequired renders it unlikely that such calculations could be sensibly carried outthroughout the UK coal industry.

However, one of the collieries, colliery Q (referred to as colliery L in bothLancaster's and McCormick's papers), offered a unique opportunity for furtherstudy. Mining methods and the colliery population had remained relatively stablefor many years. It had been one of the Pneumoconiosis Field Research (PFR)collieries (HURLEY et al., 1982) and, as part of that research, detailed records ofthe working histories of each man who worked at the colliery between 1955 and1985 were available. Extensive studies of noise exposures and sound pressurelevels had been made between 1974 and 1985 by both British Coal ScientificDepartment and the Institute of Occupational Medicine. An audiometric survey ofthe colliery Q workforce was carried out by British Coal Medical Services in 1986.

This report describes a study designed to assess the hearing levels of coalminers atcolliery Q in relation to age and noise exposure. It was restricted to theexamination and analysis of existing information and the results are presented inthis report together with details of the comparisons of measured and estimatednoise exposures described by McCORMICK (1987) which were used as a feasibilitystudy for the present work. The specific aims of this research were to:

(i) estimate lifetime occupational noise exposures of colliery Q coalminers forwhom audiometric measurements were available;

(ii) compare the hearing abilities of colliery Q workers with those predicted onthe basis of their age and estimated noise exposure;

(iii) examine the relationships between hearing level and noise exposure aftertaking account of age.

2. PRELIMINARY INVESTIGATIONS OF THERELATIONSHIPS BETWEEN MEASURED AND ESTIMATED NOISE

EXPOSURES

Between September 1983 and March 1984 British Coal Scientific Departmentmeasured the noise exposures of 10 colliery Q mineworkers (LANCASTER, 1986).Before the start of the present study a short investigation was carried out todetermine whether these measured noise exposures corresponded with estimatednoise exposures based on Scientific Department Noise Zone Measurements andPneumoconiosis Field Research (PFR) manpower records (McCORMICK, 1987).

The occupational noise exposures of the 10 men were measured continuously usingpersonal sampling techniques between September 1983 and March 1984. Theseexposures were expressed as a six month cumulative Leq.

Employment records of the 10 individuals were extracted from the PFR attendancerecords (Section 3.2). The numbers of shifts attended by each man and theoccupational groups the individuals were assigned are given in Table 2.1 Eachoccupational group was divided into a series of work activities and the noise levelsassociated with the activities obtained from the Scientific Control Noise ZoneMeasurements (see Section 3.1). Fractional doses and 8 hour Leq's wereestimated using the formulae given in Section 3.2. An example of thecalculation of an 8 hour Leq for one occupational group (face officials) from workactivities and fractional exposures is given in Table 2.2 Appendix 1 gives thisinformation for the other nine occupations involved.

The measured and estimated noise exposures, expressed as Leq's, are compared inTable 2.3 In general, agreement is good with exposure estimates being similar tothe measured values. There are, of course, a number of discrepancies, thelargest of which was associated with the mobile electrician. This individualworked considerable overtime and no record of this was kept in the PFRmanpower record system. There were, however, no systematic differences betweenthe measured and calculated Leq's.

These men covered a wide range of coalmine occupations and it was concludedfrom this preliminary study that reasonable estimates of long term exposures tonoise could be made from the PFR attendance records, Scientific Control NoiseZone Measurements (supplemented by other available noise measurement data asrequired) and a detailed knowledge of the work activities associated with eachoccupational group.

3. METHODS

3.1 Noise measurements available for study

Noise levels at colliery Q colliery were monitored by the Institute of OccupationalMedicine and Scientific Department between 1973 and 1975. Routinemeasurements of noise have been made by Area Staff from 1982 to enable noisezones to be defined. Sound pressure level measurements were made by ScientificDepartment in 1974 when a Bruel and Kjaer (B&K) 2209 precision grade SoundLevel Meter (SLM) was used on the surface and a Dawe 1419B industrial gradeSLM was used for underground measurements. All Institute measurements weremade using a B&K 2206 precision grade SLM. The Routine Noise Zonemeasurements have been made using Dawe 1405C industrial grade SLM's.

To calculate the noise exposures associated with some occupations (see below) itwas necessary to obtain noise data from machines for which no in situmeasurements were available at colliery Q. Information on noise emissions fromthese machines was supplied by Scientific Department from measurements made atother collieries around the country.

3.2 Formation of Noise Occupational Groups andAssignment of Sound Pressure Levels (Leq)

The attendance record system used in the Pneumoconiosis Field Research at collieryQ was maintained from 1955 to 1985. It was based on a series of occupationalgroups (OG's) which enabled workers' working histories to be charted for thepurpose of calculating dust exposure. Individuals were assigned to occupationalgroups from information given in colliery time sheets. The records were updatedweekly until 1981. Thereafter, quarterly summaries were recorded.

Occupational Groups were defined to satisfy the needs of a dust researchprogramme and consequently required modification for use in noise exposurestudies. Each OG comprised men with nominally similar dust exposures whocarried out similar work. Face workers were classified according to theiroccupation and the face in which they worked. Workers elsewhere undergroundand on the surface were grouped simply by the type of work they carried out.

In the present study all dust occupational groups have been reclassified in terms ofnoise occupational groups. In the first place noise occupational groups whichconsisted of men carrying out similar work using similar machinery were formedfrom the dust OGs. These noise groups were further split to allow for travellingtime. colliery Q operated an extensive diesel hauled locomotive system in theHigh Main Seam. Travelling times reached a maximum of 92 minutes for thereturn journey. To allow for the effect on the shift pattern all OG's which werelocation specific were categorised into one of four noise sub-groups dependent onthe length of travel involved and an average time allocated for travel. Thesub-groups were:

00 - No Man-rider travel e.g. pitbottom groups or <10 minutes - groups ofmen working at Waterloo, Low Bright, Main Bright plus some High Hazlegroups.

01 - 6 km return trip. Time allocation 23 minutes.

02 - 6-12 km return trip. Time allocation 46 minutes.

03 - + 12 km return trip. Time allocation 77 minutes.

Groups which were not specific in location were allocated to group 02.

For the purposes of deriving the 8 hour Leq for each occupational group theworking shift was divided into series of time periods believed to be representativeof a normal work pattern. No allowance was made for breakdowns or otherstanding time but travelling time was included. A sound pressure level wasassigned to each period from the mean of all relevant noise measurements (Section3.1). Appendix 1 gives examples for those occupations concerned in thepreliminary work. The fractional dose (f) for each period was calculated fromthe following formula (DEPARTMENT OF EMPLOYMENT, 1972)

f = t/g antilog 0.1 (L - 90)where t = Time of period in hours

L = sound pressure level dB(A)

The sum of the fractional doses gave the 8 hour Leq by the relationship:

Leq = 90 + 10 Iog10

3.3 Calculation of Noise Exposures

PFR working histories of the individuals being studied were restated in terms oftime in each noise occupational group. Using the values of Leq assigned to eachnoise occupational group and the noise working histories an average Leq(Leqave)was calculated for each individual from the following expression:

r r nI iLeq j - 90lI £T j x ant i 1 og, Q | |I I I

Leqave=90 + 10 log, 0 I l 10 JIII J^i

where T; time (yr) in OGf, Leqj is Leq in OGj.

For the purposes of investigating relationships between hearing level and noiseexposure, noise immission levels (NIL) were also calculated for each man using theequation

NIL = Lea ,̂ + 10 log,0 (T)

where T = exposure period in years.

Exposures were calculated for all men who had worked for more than 75% oftheir working life from the age of 18 and more than two years at colliery Q.

3.4 Audiometry

Audiometry was carried out by British Coal Medical Services between October andDecember 1986 using a mobile 4 booth audiometry unit. Scientific Departmenttested the site for noise which was found to meet standard requirements (HSE,1978).

Before the survey the Colliery Manager wrote to each employee inviting him toattend the survey. Any man not wishing to attend returned a form indicating hisrefusal. Those wishing to be tested were given appointments by the SafetyOfficer on a daily basis. A total of 765 persons out of the mine population of878 was surveyed.

Approximately five minutes "training/ familiarisation* was given to each group priorto audiometry. At administration each man was asked whether he workedunderground or on the surface. He was also asked whether the test was beingcarried out before, after or mid shift.

The audiometers were calibrated immediately prior to the survey and were found tomeet specifications at the end of the study.

Testing was carried out with four, three or two patients per session. Selfrecording 'Bekesy' audiometry was carried out using Peters equipment. Eightfrequencies per ear were tested - the left ear first. A final check was thenautomatically carried out to re-check 1kHz in the left ear.

All individuals were categorised according to the HSE (1978) categories (Tables 3.1and 3.2). Those men categorised 5 (normal) were informed that their hearingwas normal. Men with Category 4 (warning), Category 3 (referral) or Category 2(one sided loss - unilateral) received a letter requesting them to see the NursingOfficer - who examined the ears, syringed where necessary, and completed aquestionnaire (Figure 3.1) for each man. (On at least one occasion a manrefused to complete the questionnaire). A total of 216 questionnaires werecompleted.

Following this clinical examination men in Category 4 were sent a 'warning' letterand no further action was taken. Men in Categories 2 and 3 were asked toattend for a further hearing test. For men whose ears had been syringed thiswas at least 48 hours later.

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For the purposes of the study the following selection rules were followed:

1. Audiograms collected using audiometer B between 10 and 12 November1986 were rejected as this audiometer was malfunctioning on these days. Sevenmen were not retested and therefore were excluded from the study.

2. For men whose ears were syringed to remove wax, only audiograms takenat least 48 hours after syringing were included. Hearing levels were not measuredfor 32 men after syringing. Accordingly these men were excluded from thestudy.

3. If a second audiogram was taken for a man for any reason, this was usedin the study, rather than the first.

4. Only male industrial staff were included in the subsequent analyses.

After these rules were applied audiograms from a total of 672 individuals wereincluded in subsequent analyses.

3.5 Statistical Methods

To investigate possible relationships between hearing level and the explanatoryvariables (age and noise exposure) subjects were grouped according to values of theexplanatory variables, and mean and median values of hearing level within groupswere tabulated. Informal comparisons of age-specific hearing levels with publisheddata [ISO/DIS 1999 (ISO, 1985); ROBINSON, 1987a] were undertaken usinggraphical displays of the tabulated data. The reference audiometric data werebased on manual audiometric techniques whereas, as described above, theself-recording audiometry was used in the present study. For valid comparisonsbetween the standards and the colliery Q data, 2.5 dB was subtracted from thepublished hearing levels to account for the differences in audiometric techniques(ROBINSON, 1988). For completeness the reference data were plotted both aspublished and after correction to self-recording audiometry levels.

The statistical significance of the relationships between age and hearing level, andalso between age, noise exposure and hearing levels, was assessed by regressionanalysis. To take account of the skewed distribution of hearing levels, and alsothe curvilinear form of relationships between hearing level and explanatoryvariables, a logarithmic transformation of hearing level was used. This took theform

transformed variable = logg (hearing level + 15),

15 dB being added to allow for the occurrence of negative hearing levels. (Thelowest value recorded was -10 dB). Fitted values obtained by regression methodswere expressed on the original scale of measurement by taking anti-logs and thensubtracting 15. (Note that anti-logs of fitted means yielded 'estimates ofpopulation medians assuming that hearing levels were lognormally distributed).Differences between observed age-specific hearing levels and published data wereassessed by estimating a 95% confidence band around the fitted curve for medianhearing level, and noting whether the published curve lay within the band or not.Confidence bands were constructed using a statistical technique known as multiplecomparison (SCHEFFE, 1959). Since a confidence band for a fitted curve isessentially an infinite set of confidence intervals over a range of values of

11

explanatory variables, the usual methods based on Student's "t" are notappropriate. Scheffe's method uses a statistic based on the "F" distribution. Inthis case, the band is at a distance of 2.45 standard deviations from the fittedcurve, instread of 1.96.

Further informal comparisons were made of the numbers of men in each age bandcategorised as Categories 3 or 4, as defined by HSE (1978) guidelines, with thosepredicted from the ISO/DIS 1999. The numbers of men whose mean hearinglevels for both ears at 1, 2 and 3 kHz exceeded nominal 30 and 50 dB as definedby HEALTH AND SAFETY COMMISSION (HSC, 1987) were also determined.

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4. RESULTS

4.1 Noise Levels and Exposures

The 8 hour Leq's assigned to the noise occupational groups are summarised inFigure 4.1. Details of the nature of the various occupational groups togetherwith their assigned Leq's are given in Appendix 2.

All assigned Leq's lay between 84 and 96 dB(A) with 70% between 89 and 92dB(A). The highest noise levels were assigned to screens operators, diesellocomotive drivers, borers and Gleithobel plough operators. These results aresimilar to those found in other British collieries (JONES, 1988).

Noise exposures were calculated for 197 men. These men had worked at leasttwo years and at least 75% of their working lives from the age of 18 to the dateof audiometry at colliery Q. Men with known exposure to over 1000 rounds ofgunfire or military service were excluded. Men with ear pathology were included.

The average noise exposures are summarised in Figure 4.2. These lay within anarrow band of noise levels [86 - 92.8 dB(A)] with 83% between 88 and 91dB(A) and estimated cummulative noise exposures were highly associated withlength of service in colliery Q.

4.2 Hearing Levels of Mineworkers at Colliery Q

Table 4.1 shows the frequency distribution of the ages of 665 of the 672 subjectsat the time of audiometric testing (October to December 1986). The mean agewas 36.6 years, the standard deviation 8.8 (for seven men the subject's age wasnot recorded).

4.2.1 Comparisons with ISO/DIS 1999

Valid ages were available for 665 of the 672 men included in this part of thestudy. These men were divided into six five year age bands (20-24, 25-29,30-34, 35-39, 40-44 and 45-49) for the purposes of comparing hearing levels withthose predicted in ISO/DIS 1999. Four men aged between 19.8 and 20 wereincluded in the 20-24 age band. The eleven men over 50 were excluded fromthe graphical comparisons described below although they were included in thesubsequent regression analyses.

Figures 4.3 to 4.8 show median hearing levels (better ear) for each age grouptogether with upper and lower quartiles and the maximum and minimum, plottedagainst the mean age for the group. Predicted median hearing levels published indocument ISO/DIS 1999 and the predicted median hearing levels corrected forautomatic audiometry are also shown for non-noise exposed persons and personsexposed at 90 dB(A). (The data on which these graphs are based are given inTable 1, Appendix 3 and Table 1, Appendix 4). Each figure corresponds to adifferent frequency. At each frequency, observed medians lie below thosepredicted. Regression analysis showed that these differences were significant atthe 5% level. The 95% confidence bands for the (hypothetical) populationmedian hearing level for colliery Q men, plotted with observed medians and

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ISO/DIS productions, are shown in Figures 4.9 to 4.14. The regression modelexplains between 4.3% and 33% of the variation in hearing level according to thefrequency. Figures 4.15 - 4.18 show median hearing levels (mean of both ears),upper and lower quartiles and the maximum and minimum also plotted against themean age of each group. These figures show the median hearing levels predictedby ROBINSON (1987a), both as published and corrected for automatic audiometry.The observed levels were similar to but slightly lower than those predicted byRobinson for a non-noise exposed population.

4.2.2 Hearing levels by Health and Safety Executive category

The Health and Safety Executive have defined five categories of hearing ability(HSE, 1978). These categories are described in Tables 3.1 and 3.2.Categorisation is based on the hearing ability of the worse ear at low and highfrequencies.

The distribution of the men in the study by age and hearing category is shown inTable 4.2. The numbers of men showing hearing loss at low and highfrequencies are shown in Table 4.3 together with the proportions of men, notexposed to noise, who would be expected to fall into these categories from thepredictions published in ISO/DIS 1999. The numbers of men fitting categories 3and 4 were similar to those predicted for a typical non-noise exposed population.

It should be noted that the HSE categories refer to worse ear whereas the ISO/DIS1999 predictions refer to better ear. There is no facility in the ISO/DIS 1999document to predict the men in category 2. With the exception of men over 45the proportions of men in the categories 3 and 4 are generally less than thosepredicted from ISO/ DIS 1999.

In general more men fit categories 3 and 4 as a result of their hearing ability athigh frequency than low frequency. This is not the case for men with unilateralhearing loss where there are approximately equal numbers of men who fit thecategories at high and low frequencies.

4.2.3 Numbers of men exceeding of HSC hearing handicap and disability criteria

The numbers of men under 50 with mean hearing levels for both ears at 1, 2 and3 kHz in excess of 30 and 50 dB (respectively, the HSC (1987) criteria forhandicap and disability) are shown in Table 4.4 together with the numberspredicted from ROBINSON'S (1987b) audiometric tables for men with no noiseexposure and men exposed to 90 dB(A). Using ROBINSON's data it is notpossible to predict percentages below 5%.

No estimates are given for men over 49 as there were too few men. As can beseen from Table 4.4 a total of 24 men had hearing levels at 1, 2 and 3 kHz ^30dB and three ^50 dB. However, of these men 11 and 2 respectively had markedunilateral hearing levels suggesting that the hearing levels were unlikely to be dueto occupational noise exposure.

As the ROBINSON estimates for the non-noise exposed group indicate low (<5%)prevalences of even hearing handicap for younger men, only comparisons for oldermen can be made between observed and expected numbers of men. However,the estimates for men exposed to 90 dB(A) enable reasonable predictions to be

15

made for ages 35-49. A total of 22 cases of ^30 dB were observed as against44 estimated from the 90 dB(A) exposed population.

4.3 Hearing Levels by Age and Noise Exposure

For this analysis further exclusions were carried out. All men with gunfireexposure (at least 1000 rounds) or military service were excluded. (Men with earpathology were included). To ensure reliable noise exposure estimates, those menwho were included were also required to have work experience of at least twoyears in occupational groups at colliery Q with assigned noise levels. In addition,this period of assigned time had to comprise at least 75% of a man's total worktime from age 18 to the date of audiometry. And, finally, the disparity, if any,between assigned time and total work time could not exceed five years.

One hundred and ninety-seven men satisfied these criteria. Some summarystatistics for these men are given in Table 4.5. On average they were youngerthan the overall group of 665 subjects, but their ages covered almost as wide arange. The average Leq measured ranged from 86 to 93 dB(A) only.

Table 4.6 shows the frequency distribution by age and noise imission level (NIL) ofthe 197 men. The positive correlation between the measures is clearly shown.The variation of mean hearing level (average of both ears) with age and NILconsidered jointly, for a range of frequencies, is shown in Tables 2 to 9 inAppendix 3. There is, in general, no evidence of a relationship between hearinglevel and NIL, within the different age categories. Regression analyses of hearinglevel upon age and NIL jointly confirm this impression; results are given in Table4.7.

The relationship between hearing level and noise exposure, adjusting for age, wasalso examined using hearing level (better ear) as response, and Leq as explanatoryvariable. The results were essentially the same. After allowing for the effectsof ageing, no significant correlation between hearing level and noise exposure inthese men was observed.

4.4 Hearing Performance of Left and Right Ears

Under the audiometric protocol adopted, the left ear was tested first at the varioustesting frequencies, then the right ear and, finally, the left ear at 1 kHz. Therewas a systematic bias between the performance of the left and right ears. Theaverage hearing levels of the left ears ranged between 0.3 and 2.5 dB higher thanthe right ears according to the testing frequency (Table 4.8). In addition, thehearing level of the left ear at 1 kHz measured initially averaged 1.7 dB higherthan that found during the repeat test of the left ear at 1 kHz.

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5. DISCUSSION

The study is based on the results of audiometric testing of 672 male workers atcolliery Q. The group is, we believe, a typical population (e.g. ISO DIS/1999;ROBINSON, 1987a). The only screening was to exclude men with obvious waxin their ears in line with standard audiometric practice.

Coalmines are not quiet workplaces. Eight hour Leq's are generally close to 90dB(A) (JONES, 1986; LANCASTER, 1986; McCORMICK, 1987, JONES, 1988).Noise measurements at colliery Q over a period of over 10 years have shown that8 hour Leq's are almost invariably close to that figure. It is therefore surprisingthat, according to the reference population used, hearing levels of colliery Qworkers are similar to or better than those predicted for typical non-noise exposedpopulations (ROBINSON, 1987; ISO 1985). Considerable effort has beenexpended to ensure that substantial systematic errors had not been introduced bythe audiometry or the analyses.

Are the reference populations inappropriate? The ISO/DIS 1999 database B wasthe best reference non-noise exposed population available at the start of the study.It is described as an example, based on subjects from Europe and North America,which is believed to be representative of an industrialised country. However, ISOrecommend that a control population from the country under consideration shouldbe used as a reference, if practicable. This information was not available for thepresent study. ROBINSON (1987a) criticises the ISO/DIS 1999 document both forits recommendation regarding the construction of a non-noise exposed populationdatabase and for technical aspects in the estimation of hearing abilities of a noiseexposed population. However, comparison of the colliery Q audiometric data withthat published by ROBINSON (1987a) also leads to the conclusion that the hearingabilities of colliery Q population as a whole are at least as good as a typicalnon-noise exposed population.

ROBINSON (1988) has recently published further information describing hearinglevels for typical non-noise and noise exposed populations at 0.5, 1, 2, 3, 4 and 6kHz. This information is a compilation of published hearing levels from anumber of studies carried out in Europe and North America.

The data for 1-4 kHz are essentially the same as those he published previously(ROBINSON, 1987a). Comparisons between the colliery Q population andROBINSON'S reference populations at 0.5 kHz fit the general pattern described sofar. The data for 6 kHz is anomalous, being the only data which suggest thatthe colliery Q men are exposed to high levels of noise. ROBINSON'S predicted6 kHz hearing levels appear to be incompatible with his lower frequency data asthey suggest that hearing levels are better at 6 kHz than at 4 kHz for non-noiseexposed populations.

This is contrary to the generally accepted pattern for presbycousis (e.g. BURNS1973). Other workers have also encountered problems in the interpretation ofaudiometric data in relation to published reference data. In 1977 BURNS et alconcluded "...that severely limited quantitative significance must be attached toabsolute hearing levels, and there should always be a sizeable control group asbaseline." More recently MALLESON (personal communication, 1988) found thatthe hearing abilities of underground train drivers were better than predicted fromreference populations on the bases of age and estimated noise exposures. There

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remains much to be done to define the hearing abilities for both non-noise andnoise exposed populations. We believe, however, that we have used the mostappropriate available reference data.

Was there a problem with the audiometry? Audiometry is not a precise technique(e.g. BURNS, 1973). Errors can arise simply from the variability of anindividual's hearing threshold but this is unlikely to cause systematic errors in apopulation of 672. Other potential sources include incorrect calibration ofequipment, noisy test booths, incorrect fitting of earphones and the individual'sjudgement of his own hearing threshold. Most of these were considered andcovered in the testing protocol. Audiometers were calibrated before the studycommenced and there were no signs of instrument drift after the work wascompleted. The noise levels in the booths were tested on site prior to the surveyand found to be within acceptable limits. The audiometry was carried out byfully trained audiometricians who were aware of problems associated with poorfitting (in any case, errors in fitting would lead to poor hearing levels beingmeasured). Problems were noted in relation to the subject's judgement ofhearing threshold but these may have led to a systematic over-estimation of thehearing levels of the colliery Q men, most of whom were undergoing their firstaudiometric test. It was found that, according to the frequency, left earsperformed, on average, between 0.3 and 2.5 dB poorer than right ears and therepeat 1 kHz test on the left ear indicated a hearing level 1.7 dB lower than thefirst test on the left ear at that frequency. This is a clear indication of alearning effect. As the test proceeds the subject's performance appears toimprove until it approaches his actual hearing ability. ROBINSON and WHITTLE(1973) noted similar learning effects in studies of audiometric techniques. Anotherpotential source of systematic error is the correction made to the standards toaccount for the differences between manual and self-recording audiometry. Thishas been reported as being small by a number of authors (e.g. ROBINSON, 1988)and the figure of 2.5 dB (ROBINSON, 1988) adopted makes little difference to theoverall conclusions.

Despite the apparent good hearing of the population in relation to the ISO/DIS1999 and ROBINSON (1987a) reference populations, a substantial number of menhad hearing abilities which were categorised as abnormal under the current HSEGuidance (HSE 1978) and a few fitted the HSC hearing handicap and disabilitycriteria. Some further work, using both ISO/DIS 1999 or ROBINSON'S (1987b)data, was therefore carried out. The predictions of HSE hearing category werebased on the information provided in ISO/DIS 1999. These predictions should belower, as the HSE categories are based on worse ear while ISO/DIS 1999 is basedon better ear. It is therefore surprising that with a non-noise exposedpopulation, aged over 35 about 40% of better ears would be categorised as'warnings' and about 10% as 'referrals'. Similar proportions of the colliery Qpopulation were in these categories on the basis of the hearing performance oftheir worse ear. ROBINSON'S (1987b) data were used to predict the numbers ofmen expected to fall into the HSC's (1987) 'handicap' category on the basis of agealone and age together with noise exposure at 90 dB(A). Again, the numbers inthe colliery Q population were not substantially different from those predicted for atypical non-noise exposed population and about a half of those expected in apopulation exposed to 90 dB(A). It is of note that a substantial proportion ofthe men fitting the handicap category suffered unilateral hearing loss which isunlikely to be occupationally induced.

19

It is, therefore, clear that, by all criteria examined the hearing abilities of thecolliery Q population was similar to those predicted for a typical non-noiseexposed population.

Is coalmining noise less damaging than surface industry noise? Noise on thecoalface tends to have a larger proportion of the energy in the frequencies belowabout 500 Hz and to be less 'peaky1 than surface industry noise of similar 'A1

weighted sound pressure level.

A number of studies (e.g. KYLIN, 1960) have shown that although noise at mostfrequencies can cause temporary threshold shift (TTS) in the 1-4 kHz range, thelower the noise frequency, the less TTS generated for a given 'A1 weighted soundpressure level. If it were assumed that TTS is indicative of possible permanentdamage, mining noise might be less damaging than noise of the same 'A' weightedlevel with relatively greater energy in the higher frequencies. In addition, duringthe UK study which led to the Department of Employment 'Code of Practice'(Department of Employment 1972) and BS 5330 (BSI 1976), it was found that thebest energy correlate with noise induced hearing loss was the L^, the 'A'weighted sound pressure level exceeded for 2 per cent of the measurement period(BURNS and ROBINSON, 1970). However, at that time, equipment to measure^A2 was larSe and bulky and a correction to permit the use of Leq wasintroduced. This correction was based on the assumption that L^2 = Leq + 3.7dB. If the actual difference between Leq and L^2 IS not 3.7 dB, the predictionof hearing loss may be incorrect. In coalmines the LA2~Leq difference has beenobserved to be around 1.5 dB. The use of the Leq may therefore haveoverestimated L^ and resulted in a greater noise induced hearing loss beingpredicted than had the actual L^2 figure been used.

The combined effects of the low frequency characteristic of mining noise and therelative constancy within any shift of coalmine noise levels could therefore, at leastpartly, explain why the mineworkers at colliery Q had better hearing levels thanpredicted by either ISO DIS 1999 or ROBINSON for age matched populationsexposed to Leq of 90 dB(A).

The relationship between hearing ability and age was clearly identifiable in thepresent study but we could not distinguish any relationship between noise exposureand hearing ability after allowing for age. This may largely be a result of thenarrow range of average noise exposure levels at the colliery with the consequentclose correlation of noise exposures with age. The hearing levels observed suggestlittle noise induced hearing loss and this too may have made it difficult to identifyany relationships between noise exposure and hearing ability after allowing for age.However, there is no doubt that excessive exposure to noise at work causesoccupational deafness (BURNS and ROBINSON, 1970; BAUGHN, 1973). Webelieve that noise control initiatives in the coalmining industry should be continuedso that occupational exposure and any consequential hearing loss is minimised.

Despite the limitations of this study its results have several substantial implications,particularly with regard to the imminent introduction of the noise controlregulations to meet the CEC Noise Control Directive. If the colliery Qpopulation were typical of the UK coal industry in general it would be clear thatthe industry would be meeting the objective of the regulation in terms of hearinglevels while not, in some instances, meeting the required noise levels.

20

Earlier unpublished studies* has also demonstrated lower than predicted hearinglevels amongst coalminers but these studies were based on small numbers ofspecially selected men. It will be necessary to carry out a number ofcomprehensive audiometric surveys of coalmine populations in a number ofcoalfields throughout the country to determine whether the results at colliery Q aretypical for coalmine workers.

This additional work would give a good indication of hearing level within theindustry but would not answer the question 'does work in a coalmine causedeafness?1 This could only be answered by a prospective study over a number ofyears. Ideally new entrants and the populations described above, including anyleavers, would be followed in such a study. Records of occupations could bemaintained relatively easily through access to payroll systems and these, inconjunction with routine Scientific Department noise measurements, might provideacceptable estimates of noise exposures for use in a prospective study.

* Dick JA, Hearing levels in the British coalmining industry. Paper presented toXVIII International congress on Occupational Health, Brighton 14-19September 1975

Dick JA, Coleman G. British Coal Internal Report, 1979

21

6. CONCLUSIONS

1. Estimated individual lifetime mean exposures (average Leq) to noise rangebetween 86 dB(A) and 93 dB(A). 83% of the men included in the noiseexposure study were exposed between 88 and 91 dB(A).

2. The hearing levels of the men were found to be substantially similar tothose predicted from typical age-matched, non-noise exposed populationsand were better than those predicted for populations exposed to noise at90 dB(A).

3. These differences from predicted hearing levels are not readily explicablefrom the data available and require further investigation.

4. After allowing for the effects of age there was no significant correlation ofhearing level with noise exposure amongst the 197 miners studied.

5. It is apparent that even amongst a non-noise exposed populationsubstantial proportions of men would be expected to fit the HSE warningand referral categories of hearing level.

6. We have no means of knowing whether colliery Q men are representativeof the UK coal industry. In view of the forthcoming noise controlregulations we recommend that a further cross-sectional study is undertakento investigate hearing levels of miners in relation to age at a number ofcollieries to assess whether the colliery Q results are typical of theindustry. We further recommend that this study should be designed toenable it to be extended to a prospective study if required.

23

ACKNOWLEDGEMENTS

The authors would like to thank colliery staff and personnel and colleagues in theInstitute of Occupational Medicine, British Coal Scientific Control and British CoalMedical Service for their help and co-operation throughout. We also thank theBritish Coal Corporation for funding the study.

24

25

REFERENCES

BAUGHN WL. (1973) Relation between daily noise exposure and hearing lossbased on the evaluation of 6835 industrial noise exposure cases. Ohio:Wright-Patterson AFB, Aerospace Medical Research Laboratory.(AMRL-TR-73-53) (EPA-550-73-001 -C)

BRITISH STANDARDS INSTITUTION. (1976) Method of test for estimating therisk of hearing handicap due to noise exposure. London: BSI. (BS 5330: 1976)

BURNS W. (1973) Noise and man. 2nd ed. London: John Murray.

BURNS W, ROBINSON DW. (1970) Hearing and noise in industry. London:HM Stationery Office.

BURNS W, ROBINSON DW, SHIPTON MS, SINCLAIR A. (1977) Hearinghazard from occupational noise: observations from heavy industry. Teddington:National Physical Laboratory. (Acoustic Report Ac 80)

DEPARTMENT OF EMPLOYMENT. (1972) Code of practice for reducing theexposure of employed persons to noise. (With correction slip 12/1/81). London:HM Stationery Office.

FACTORIES (1974) Woodworking Machines Regulations 1974. London: HMStationery Office. (SI No.903)

HEALTH AND SAFETY COMMISSION. (1987) Prevention of damage to hearingfrom noise at work: draft proposals for regulations and guidance. London: HMStationery Office.

HEALTH AND SAFETY EXECUTIVE. (1978) Audiometry in industry. Reportof the HSE Working Group on Audiometry. Discussion document. London: HMStationery Office.

HURLEY JF, BURNS J, COPLAND L, DODGSON J, JACOBSEN M. (1982)Coalworkers1 simple pneumoconiosis and exposure to dust at 10 British coalmines.British Journal of Industrial Medicine; 39: 120-127

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION. (1985)Acoustics - assessment of occupational noise exposure and estimation ofnoise-induced hearing impairment. Draft. Switzerland: ISO. (ISO/DIS 1999.2)

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION. (1975)Assessment of occupational noise exposure for hearing conservation purposes.Switzerland: ISO. (ISO 1999-1975)

JONES K. (1986) Personal noise exposure. Colliery Guardian: 136-140

JONES K. (1988) Sound pressure level zones - their use for monitoring noiseexposure. Colliery Guardian: 126-129.

KYLIN B. (1960) Temporary threshold shift and auditory trauma followingexposure to steady-state noise. An experimental and field study. ActaOto-Laryngologica; (suppl.152):

26

LANCASTER GK. (1986) Personal noise exposure. Part 2: A summary of asix-month survey at three collieries. Colliery Guardian; 213-216

MCCORMICK G. (1987) Personal noise exposure. Colliery Guardian; 488-491

ROBINSON DW. (1987a) Noise exposure and hearing - a new look at theexperimental data. Bootle: Health and Safety Executive. (HSE Contract ResearchReport No.l)

ROBINSON DW. (1987b) Tables for the estimation of hearing impairment due tonoise for otologically normal persons and for a typical unscreened population.Southampton: Institute of Sound and Vibration Research. (ISVR Contract ReportNo.87/4)

ROBINSON DW. (1988) Threshold of hearing as a function of age and sex fortypical unscreened population. British Journal of Audiology; 22: 5-20

ROBINSON DW, WHITTLE LS. (1973) A comparison of self-recording andmanual audiometry: some systematic effects shown by unpractised subjects.Journal of Sound and Vibration; 26: 41-62

SCHEFFE (1959) The analysis of variance. New York. John Wiley.

27

TABLE 2.1 PFR Occupational Group records for the10 men with measured noise exposures

Recorded Occupational Group

Worker

A

B

C

D

E

F

G

H

I

J

Key

010500103201044010490033001053005270052901058

Attendance(Shifts) Sept. 1983 Oct-Dec. 1983

127 01050

134 01032

133 01044

131 01049

133 01044

124 00330

94 00330

126 01053

130 00527

135 00529

Face OfficialsLoco DriversBelt AttendantOnsettersFace TradesmenGeneral WorkersM/c Operators and CheckersReturn Rippers Al9's FaceDevelopment Worker - High

01050

01032

01044

01049

01044

00330

00330

01053

00527

01058

Al9's Face

Hazles

Jan-Mar. 1984

01050

01032

01044

01040

01044

00330

00330

01053

00527

01058

28

TABLE 2.2 An example of the calculation of8 hour Leq for an occupational group from work

activities and fractional exposures

Work Act ivity

Travel in LocoCarriages/manrider

Walking time/snap time

Loader Gate

Loader Gate Ripping

Loader Gate Stable Hole

Main Face Machine DEDMT

Face Panzer

Supply Gate Sumper

Supply Gate Ripping

Supply Gate Power Pack

Durat ionofExposure(mini

130

50

50

20

30

30

60

25

20

20

435

SPLdB(A)

89.8

80.0

89.6

90.4

91.1

97.3

86.6

97.1

90.9

86.6

Fract ionalExposure

0.258

0.010

0.094

0.046

0.080

0.335

0.057

0.267

0.052

0.019

1.218

Est imatedfromspecialsurvey

Leq 8 hr = 90.9 dB(A)

29

TABLE 2.3 Comparison of estimated and measured Leq'sfrom IOM manpower records and noise measurements

Equivalent continuous sound levels

Worker

A

B

C

D

E

F

G

H

I

J

Occupat ion

Face Deputy

Loco Driver

Belt Attendant

Belt Attendant

Onset ter

Face Fitter

Mobile Electrician

Dust Sampler

Machine Op Propper

Developer

LeqCalculated-8 hr

est imated90.9

94.3

87.9

87.9

92.2

91.2

91.2

87.7

93.0

90.091.5

rdBCA1)!Measured-6 month

90.0

94.6

86.6

89.0

89.6

87.6

97.8

84.9

89.9

87.891.6

30

TABLE 3.1 HSE Hearing Level Categories

Category Basis/Criteria

1 Comparison of Sequential Audiograms(Rapid Deterioration)Sum of Hearing Levels for either ear, lowor high frequencies>30dB - period between Audiometry <3 yr>45dB - period between Audiometry >3 yr

2 Comparison of Ears (Unilateral Loss)Difference between ears, low frequencies >45dBDifference between ears, high frequencies >60dB

3 Hearing Levels, Either Ear, Age RelatedSum of hearing levels exceed referral criteria

4 Hearing Levels, Either Ear, Age RelatedSum of hearing levels exceed warning criteria

5 Cases not meeting above criteria'Normal' hearing

31

TABLE 3.2 Referral and Warning Criteria

Sum of hearing levels

Agein vrs

20-2425-2930-34

35-3940-4445-49

50-5455-5960-6465-

0.5. 1. 2WarninglevelCat 4

454545

485154

57606570

kHzReferrallevelCat 3

606672

788490

90909090

3. 4. 6 kHzWarninglevelCat 4

454545

546066

7487100115

ReferrallevelCat 3

758799

111123135

144144144144

TABLE 4.1 Frequency distribution of ages of 665 subjects at Colliery Q(The mean age and standard deviation within each age group,

used in graphical displays, is also shown).

Age (years) wto

19-24 25-29 30-34 35-39 40-44 45-49 50-54 ^55

No. of subjects 88 97 94 114 130 131 9 2

Mean age (s.d.) 22.5(1.6) 27.7(1.4) 32.5(1.5) 37.8(1.4) 42.4(1.4) 47.5(1.3) 51.0(0.9) 59.6(4.8)

TABLE 4.2 Distribution of men in HSE hearing ability categories by age

HSE category Numbers (%) of menof hearingloss

Age group

20-2425-2930-3435-3940-4445-49Over 50Al 1 men

2

(uni lateral)

3( 3.4)10(10.1)12(12.8)12(10.5)10( 7.5)17(12.9)5(41.7)69(10.3)

3

(referral)

6( 6.8)2( 2.0)1( 1.1)5( 4.4)9( 6.8)18(13.6)041( 6.1)

In category

4

(warning)

17(19.3)19(19.2)30(31.9)40(35.1)47(35.3)57(43.2)7(58.3)

217(32.3)

5

(normal)

62(70.5)68(68.7)51(54.2)57(50.0)67(50.4)40(30.3)0

345(51.3)

Total

88999411413313212

672

u>

TABLE 4.3 Measured and predicted proportions of men in HSE hearing abilitycategories split by frequency and age

HSE categoryof hearing 2(uni lateral )

High1 Low2

Age erouo

20253035404550All

- 24- 29- 34- 39- 44- 49and overmen

meas-'

3.48.110.65.25.36.83.37.0

meas

1.19.17.47.06.09.13.37.3

% of men in category3(referral)

High Lowmeas^

5.72.00.03.56.0

12.904.1

ored4

n.a.9.28.79.210.012n.a.n.a.

meas ored

11123201

.1 n.a.

.0 <1

. 1 <1

.6 <1

.0 <1

.3 <1

.0 n.a.

.9 n.a.

4(warning)High Low

meas

19.319.230.934.235.343.258.328.8

ored

n.a.2936363841n.a.n.a.

meas

002.15.26.05.30.03.4

ored

n.a.4.86.67.79.412n.a.n.a.

n.a. - not applicable1 - high frequency (based on sum of hearing loss at 3, 4 and 6 kHz)2 - low frequency (based on sum of hearing loss at 0.5, 1 and 2 kHz)3 - measured H of men4 - % men predicted from ISO DIS 1999 (Better ear)

u>

35

TABLE 4.4 Observed and Predicted exceedancesof HSE hearing handicap and disability criteria

Numbers of men with handicapof disability

Observed Predicted1

Age Group

19-24

25-29

30-34

35-39

40-44

45-49

No. of Menin Group

88

99

94

113

138

131

Non-noise 90 dB(A)Exposed Leq

Handicap^ Disability^ Handicap Handicap

0

0

1 (1)

4 (4)

6 (4)

12 (9)

0

0

0

0

1 (1)

2 (2)

7 (6)

15 (11)

9 (7) 23 (18)

Figures in brackets are percentages

Predictions based on ROBINSON (1987a) The published data do not permitresolution of predictions below 5% of the population under study. The proportionsof men predicted as having disability were less than 5% for all age groups understudy, both non-noise exposed and

Handicap : mean hearing levels for both ears at 1, 2 and 3 kHz exceeding 30dB.

Disability : mean hearing levels for both ears at 1, 2 and 3 kHz exceeding 50dB.

36

TABLE 4.5 Summary statistics of the ages, and noise exposuremeasured (noise imission levels (NIL) and Leq) of

197 men at colliery Q

Characterist icStatistic

Mean

Std.Dev.

Min

Max.

Age (years)

33.5

8.5

20.6

50.6

NIL CdB)

100.

3.

91.

106.

3

6

6

4

Leq (dB)

89.4

1.2

86.2

92.8

37

TABLE 4.6 Joint frequency distribution of ages andnoise imission levels (NIL) of 197 men

NIL (dB)Age (vears)

<30

30-40

>40

<96

24

0

0

-98

29

2

0

-100

24

7

0

-102

5

29

1

-104

2

19

27

>104

0

5

23

38

TABLE 4.7 Anti-logs of regression coefficients of age andnoise imission levels (NIL), by frequency, with

statistical significances in brackets

Frequency (kHz) Age effect (per 10 years) NIL effect (per 10 dB)

0.25 x 1.13 (P = 0.04) x 0.88 (P =0.37)

0.5 x 1.18 (P = 0.02) x 0.79 (P = 0.17)

1 x 1.25 (P - 0.002) x 0.84 (P - 0.33)

2 x 1.28 (P = 0.003) x 0.87 (P = 0.50)

3 x 1.26 (P = 0.003) x 1.09 (P - 0.64)

4 x 1.34 (P <0.001) x 1.15 (P = 0.42)

6 x 1.30 (P <0.001) x 0.89 (P = 0.44)

8 x 1.37 (P <0.001) x 0.85 (P - 0.30)

TABLE 4.8 Differences in hearing levels betweenleft and right ears

Frequency (KHz) 0.25 0.5

Difference (Right-Left )dB -1.6(0.4) -0.6(0.4) -0.7(0.4) -0.7(0.4) -1.4(0.5) -2.0(0.6) -2.5(0.6) -0.3(0.6)

Figures in brackets are standard errors

40

41

FIGURE 3.1 Audiology Questionnaire (Page 1)

NATIONAL COAL BOARDMEDICAL SERVICE

AUDIOLOGY QUESTIONNAIRE

Colliery/Workplace Date

Name DOB Check No....(Blocn Letters)

Address Name of G.P..

Interviewer Audiogram No

1. Present Occupation No. of years

2. Do you have to shout to make yourself heard at work?

(a) All the time I I

(b) Occasionally I I

(c) Never I |

3. Prior to your present job, have you ever worked on a noisy job. where you had to shout to makeyourself heard? ^_^

YES I I NO I I

Firm: Job: Length of time:

Firm: Job: Length of time:

4. Have you ever worn ear protection? YES I I NO I I

Which job

Type Length of time

5. Have you ever used

(i) A rifle? YES I I NO I I

(ii) Any other gun? YES I I NO I I

State type of gun When?

How many rounds 10/100/1,000/10,000

6. Have you ever been in a explosion? YES I I NO I I

What?

When?

What was the result?

7. Is your hobby any of the following; SHOOTING/DISCOS/BRASS BAND/ORCHESTRA PLAYINGMOTOR CYCLING/MOTOR RACING?

Nca MM UHH m mmss P.T.O.

42

FIGURE 3.1 Audiology Questionnaire (Page 2)

-2-

8. Have you ever been unconscious? YES I I NO I I

When For how long

9. Have you ever had any of the following?

MEASLES/MUMPS/MENINGITIS/CHICKEN POX/SCARLET FEVER/EAR INFECTION

10. Have you ever had Streptomycin or Quinine? YES I I NO I I

11. Do you have noises in your ears after work?

What are these noises like?

How long do the noises last?

12. Is your hearing normal?

If not which ear is affected?

13. Can you hear better or wors

14. Do you suffer from wax in your ears?

15. Have you had any discharge trom your ears?

16. Have you had any operations on your ears?

YES D NO D

st?

i?

rse in noisy

your ears?

MINUTES/HOURSi i i i

LEFTD

surroundings?

YES

BETTE

YES

uRIGHT

nD

NO

DWORSE

NO

U

DD

BOTH 1 1

YES I I NO

YES I I NO

17.

18.

Has your eardrum ever been punctured?

When:

Is there any deafness in your family?

Which relative

YES

Which ear:

YES

l_l

D

NO LJ

NO D

D19. Suitability for audiometry:

(i) Wax? YES I I NO I I if YES RIGHT | | LEFT

(ii) Others - e.g., ACUTE OTITIS / SINUSITIS / HAY FEVER / COLD / INFLUENZA / DERMATITIS

(Ml) Drums condition

(iv) Last exposure to noise WORK / HOBBY / TRAVELLING Hrs. ago

20. REMARKS:

43

FIGURE 4.1 Distribution of Noise Occupational Groups by Leq.

3<H

o-0

V)0.3OocoUJ(A

Oz

25 ̂

20 H

15

10

FACE

DEV

E/USS5S-3SURFACE

84 85 86 87 88 89 90 91

Leq. ( d B A )

92 93 94 95 96

44

FIGURE 4.2 Distribution of men by average Leq.

SO-i

45-1

40-

35-

v 3B-

tu25-

k.O. 20H

Oz

15-

10-

86.0 66.5 87.0 87.5 88.0 88.5 W.8 89.5 M.O 90.5 91.0 91.5 92.0 92.5 93.0

A V E R A G E L«q

45

FIGURE 4.3 Comparison with ISO/DIS 1999;Median hearing levels for colliery Q men vs age

0.5 KHz

100-

80-

00 60-

UJ

UJ_1

o40-

tr<:LJ 20-

0-

-2020 25

NN

30 35 40AGE(YEARS)

45 50

median, quartiles and range of hearing levelsfor age group

ISO/DIS 1999 prediction, uncorrectedISO/DIS 1999 prediction, corrected by -2.5 dB

NN - Non-noise exposed population (same as 90 dB(A)exposed at 0.5 kHz)

46


1 KHz

100'

80-

CD 60-"D

40-

UJ

LJ_J

OzI—I

^ 20-

0-

-2020

NN

25 30 35 40AGE(YEARS)

45 50


ISO/DIS 1999 prediction, unconnectedISO/DIS 1999 prediction, corrected by -2.5 dB

NN - Non-noise exposed population (same as 90 dB(A)exposed at 1 kHz)

47


2 KHz

100

80-

00 60-

LJ

LJ_J 40-

O

I-HIT

LJ 20-

0-

-20'20 25 30 35 40

AGE(YEARS)45

I

90 dB'(A)

NN

50



NN - Non-noise exposed population

48


3 KHz

100

80-

CD 60--O

LJ>UJ

40-

20-

0-

-2020

90 d B ( A )

NN

25 30 35 40AGE(YEARS)

45 50




49


4 KHz

100-

80-

03 60-"O

LJ>

O

40-

UJ 20'

0-

-20-20 25

I

30 35 40A G E ( Y E A R S )

90 dB(A)

NN

45 50




50


6 KHz

100-

80-

00 60-

>UJ

O

40-

UJ 20-

0-

-20-20

I

25 30 35 40AGE(YEARS)

45

90 d B ( A )

NN

50


ISO/DIS 1999 prediction, unconnectedISO/DIS 1999 prediction, corrected by -2.5 dB


51

FIGURE 4.9 Hearing level (Better ear) vs age

0.5 KHz

4-0

32-

00 24-

UJ—I 16-

O

IT

bJ 8-

0-

-8-20 25 30 35 40

A G E ( Y E A R S )

NN

45 50

I

observed median

95% confidence band for (hypothetical) populationmedian hearing level underlying colliery Q data

ISO/DIS 1999 prediction, uncorrected

ISO/DIS 1999 prediction, corrected by -2.5 dB

NN - Non-noise exposed population (same as 90 dB(A)exposed at 0.5 kHz)

52


1 KHz

40-

32-

DQ 24-

_JLJ

LoJ16-

O-z.I— I

LJ 8'

0-

-820 25 30 35 40

AGE(YEARS)

NN

45 50

I

observed median


ISO/DIS 1999 prediction, unconnected


NN - Non-noise exposed population (same as 90 dB(A)exposed at 1 kHz)

53


2 KHz

40'

32-

03 24-"D

LJ

LJ_l

O

I—icc

16-

8-

0-

-8-20

I +

90 d B ( A )

NN

25 30 35 40AGE(YEARS)

45 50

Iobserved median


ISO/DIS 1999 prediction, uncorrected



54


3 KHz

40

32-

03 24-

LU

LU_l

O

16-

LJ 8-

0-

20 25 30 35 40

AGE(YEARS)45

90 d B ( A )

NN

50

Iobserved median



BO/DIS 1999 prediction, corrected by -2.5 dB


55


4 KHz

40'

CD 24-

UJ>

16-

UJ 8-

0-

-8-

I

20 25 30 35 40 45A G E ( Y E A R S )

90 d B ( A )

NN

50

Iobserved median




NN - Non-noise exposed population *-.

56


6 KHz

40

32-

m 24--o

LJ

UJ_lo

16-

8-1

0-

-8-20 25

90 d B ( A )

NN

30 35 40A G E ( Y E A R S )

45 50

Iobserved median





57

FIGURE 4.15 Comparison with ROBINSON (1987)Median hearing levels for colliery Q men v age

1 KHz

100

BO-

CD 60"D

UJ>

ozM(T

40-

20-

0-

-20-20

—i—25

—r—30

—r~35

AGE(YEARS)

—,—40

—i—45

90 d B ( A )NN

50


Predicted hearing levels from ROBINSON (1987) - unconnectedPredicted hearing levels from ROBINSON (1987) - corrected by-2.5 dB


58


2 KHz

100

80-

00 60-

>LJ_J 40-

O

tr

20-

0-

-2020 25 30 35 40

AGE(YEARS)45

90 d B ( A )

NN

50


Predicted hearing levels from ROBINSON (1987) - unconnectedPredicted hearing levels from ROBINSON (1987) - corrected by-2.5 dB


59


3 KHz

100'

80-

00 60-

LoJ>

CD

40-

CC<UJ 20-

0-

-20-25 30 35 40

AGE(YEARS)45

90 d B ( A )

NN

50


Predicted hearing levels from ROBINSON (1987) - uncorrectedPredicted hearing levels from ROBINSON (1987) - corrected by-2.5 dB


60

FIGURE 4.18 Comparison with ROBINSON (1987)Median bearing levels for colliery Q men v age

4 KHz

100'

80-

CD 60--o

>UJ

o:

40-

20-

0-

-20

90 d B ( A )

NN

20 25 30 35 40AGE(YEARS)

45 50


Predicted hearing levels from ROBINSON (1987) - uncorrectedPredicted hearing levels from ROBINSON (1987) - corrected by-2.5 dB

NN - Non-noise exposed) population

APPENDIX 1

Preliminary investigation of measured and estimated noise exposures at colliery Qwork activities and fractional noise exposures for the occupations concerned.

Face Tradesmen - OG 00330

Work Act ivity


Face Panzer

Walking Time/Snap Time

Main Face Machine Decmt

S/G Sumper

L/C AFC Drive

S/G Stage Loader

S/G Power Pack

Durat ionofExposure(min)

130

75

50

30

30

30

30

30

435

SPLdB(A)

89.8

86.6

80.0

97.3

97.1

91.1

90.4

86.6

Fract ionalExposure

0.258

0.071

0.010

0.336

0.321

0.081

0.069

0.029

1.332


Leq = 9 1 . 2 dB(A) 8 hr

Gen Workers - OG 01053

Work Activity

Travel in LocoCarriages/manriders

Snap time

Walking time

O/bye Machinery General

Conveyor Roads


130

20

50

100

135

435

SPLdB(A)

89.8

80.0

80.0

91.5

80.0

Fract ionalExposure

0.258

0.004

0.010

0.294

0.028

0.594


Leq =87.7 dB(A) 8 hr

Loco Driver - OG 01032

Work Act ivity

Driving Loco

Pitbottom No. 1

Loco Garage

Snap time


120

150

145

20

435

SPLdB(A)

98.0

95.0

85.0

80.0

Fract ionalExposure

1.577

0.988

0.096

0.004

2.665


Belt Attendants - OG 01044

Work Act ivity

Travel in LocoCarriage/manrider

Snap Time

Operators Position

Cleaning Mech/ElectMachinery

Cleaning T/P Chutes

Leq =87.9 dB(A)

Rippers - OG 00529

Work Act ivity

Durat ionof SPLExposure dB(A)(mini

60 89.8

20 80.0

235 85.9

60 91.3

60 90.1

8 hr

Durat ionof SPLExposure dB(A)(mini

Fract ionalExposure

0.129

0.004

0.192

0.169

0.128

Fract ionalExposure


Snap Time

Supply Gate Ripping

130 89.8 0.258

20 80.0 0.004

285 90.9 0.730



435 0.992


Development Workers - OG 01058

Work Act ivity

Travel in LocoCarriages/Manrider

Snap Time

Machine Cutting/Drill

Gen. Work in Heading

Leq =91.5

Onsetters - OG 01049

Work Activity

Materials

Manriding

Skip Winding

Ambient Level

Snap Time

Durat ionof SPLExposure dB(A)(min)

130 89.8

20 80.0

ing 60 96.7

225 90.9

435

dB(A) 8 hr

Durat ionof SPLExposure dB(A)(min)

4 104.0

1 104.0

200 91.0

210 88.0

20 80.0

435

Fract ionalExposure

0.258

0.004

0.585

0.577

1.424

Fract ionalExposure

0.209

0.052

0.551

0.276

0.004

1.092



Repairers - OC 01040

Work Activity

Travel in LocoCarriage/manrider

Snap Time

General U/G Ambient

Jigger Pick

Dri 1 1 ing


60

20

335

10

10

SPLdB(A)

89.8

80.0

91.3

107.0

97.9

Fract ionalExposure

0.129

0.004

0.941

1.044

0.129


435 2.246

Leq =93.5

APPENDIX 2

Noise Occupational Groups and their assigned Leq's

TABLE 1 APPENDIX 2

Colliery Q - Summary of OG Allocation to

NoiseGroup

Nl

N2

N3

N4

N5

Noise Groups and Calculated 8hr LEQ

TravelDescription Sub-Grouo

Machine Operators(Shearer Faces)

L/C Stablemen(Handfilled)(Shearer Faces)

L/C Stablemen(Handfilled)(Shearer Faces)

Facemen(Shearer Faces)

Ripper1 s(Convent ional)(Unclassified Site)

00

01

03

00

01

03

01

03

01

03

01

02

03

8hr LEQdBfA)

87.6

87.6

87.9

89.6

89.6

89.7

88.6

88.9

87.7

87.4

90.7

90.6

90.6

Values

OG's

F436

F113/F213/F470/F480F536/F109

F88/F187

F345

F110/F114/F214/F469

F89/F184

F111/F115/F215/F481

F90/F176/F177/F185F186

F112/F116/F216

F91/F188

F46/F47/F81/F98F121

F19/F20/F44/F45

F16/F17/F18/F21/F75F85/F99/F167

N6 Face Craftsmen 03 91.0 F108/F330

TABLE 1 APPENDIX 2 (contd)

NoiseGroup Description

Travel 8hr LEQSub-Group dB(A) OG's

N7 L/C Rippers(Convent ional)

01 91.1 F146/F149/F151/F156F198/F201/F202/F223F267

02 90.9 F125/F137/F140/F143F217/F229/F235/F245F251/F255/F258/F259F260/F261/F277/F295F310/F320

03 90.7 F122/F128/F131/F154F159/F165/F169/F271F278/F279/F285/F290F300

N8 T/G Rippers(Conventional)

01

02

03

90.8 F147/F148/F150/F152F153/F157/F158/F197F199/F200/F203/F224F268/F524

90.6 F126/F127/F138/F139F141/F142/F144/F145F218/F230/F236/F246F254/F262/F296/F311F321/F342

90.5 F123/F124/F129/F130F132/F133/F135/F136F155/F160/F161/F164F166/F170/F171/F272F280/F286/F291/F301F306/F364/F370/F372

N9 Machine Operators(Trepanner Faces)

01 91.9 F205/F209/F225/F241

02 91.7 F219/F231/F237/F247F256/F263

03 91.6 F189/F273



TravelSub-Group

8hr LEQOG's

N10 L/C Stablemen(Handfilled)(Trepanner Faces)

01

02

03

00

90.5 F206/F210/F226/F242F269/F326/F379/F496F501/F506/F511/F516F521/F526/F531/F540

90.5 F220/F232/F238/F248F253/F264/F298/F313F318/F323/F344/F389F397/F467/F474


90.2 F394/F462

Nil T/G Stableman(Convent ional)(Trepanner Faces)

00

01

02

03

89.6 F395/F464

89.7 F207/F211/F227/F243F270/F327/F380


89.5 F191/F192/F275/F283F289/F294/F304/F309F338/F351/F362/F369F385/F385/F404/F418F424/F449


NoiseGroup

N12

N13

N14

TravelDescription Sub-Group

Machine operators 00& Proppers(Trepanner Faces, 01Combined Group)

02

03

General Workers 02

03

L/C Face End Prep. 01(Retreat TrepannerFaces) 02

03

8hr LEQdBfA)

88.2

88.3

88.5

88.6

87.0

87.0

90.3

90.2

90.2

OG's

F333/F393/F463

F208/F212/F228/F244F325/F378/F490/F497F502/F507/F512/F517F522/F527/F532/F541

F222/F234/F240/F250F257/F266/F297/F312F317/F322/F343/F355F388/F398/F431/F453F458/F475/F485

F193/F276/F281/F287F302/F292/F307/F336F349/F360/F366/F373F3 83/F403/F40 8/F4 1 7F423/F448

E13/E19/E22/E33/E42E43/E53/E54

F284

F328/F347

F315/F346

F339/F348/F352/F401F415/F422/F426/F446

N15 L/G Face EndPackers/Prep.(Trepanner Faces)

00 90.3 F334

01 90.3 F489

02 90.2 F358/F412/F430/F451F457/F484

03 90.2 F368/F374/F428


NoiseGroup

N16

N17

N18

Travel 8hr LEQDescription Sub-Group dB(A)

T/G Face EndPackers/Prep.(Trepanner Faces)

Heading Team (Bored,Fired, Power Loaded& Pneumatic Stower)

Heading Team (Bored,Fired & Power Loaded)

00

02

03

03

00

02

03

89.6

89.6

89.5

92.3

91.6

91.5

91.4

OG's

F335

F359/F413/F432/F454F486/F493

F409

F305

F331/F332/F445/F442

F356/F357/F411/F414F429/F433/F452/F455F456/F483/F487/F494

F363/F367/F371/F410F420/F421/F427

N19 L/C Rippers (Bored,Fired, Power Loaded)

00 91.0 F391/F434/F461

01 91.0 F376/F468/F478/F495F500/F505/F510/F515F520/F525/F530/F539

02 90.9 F341/F386/F396/F466F473

03 90.6 F381/F406

N20 T/G Rippers(Ripping Machine)

00 91.3 F392/F438

01 91.3 F472/F482/F492/F499F504/F509/F514/F519F529/F534/F538/F543

02 90.9 F460


NoiseGroup

N21

N22

N23

N24

N25

N26

N27

TravelDescription Sub-Grouo

T/G Face End Prep.(Trepanner, RetreatFaces)

T/G Stablemen(2nd Machine -Shearer)

T/G Stablemen(2nd Machine -Waffler)

T/G Rippers(Bored, Fired,Power Loaded)

Heading Team(Dosco)

L/C Rippers(Ripping machine)

L/C Face End Prep.(Gleithobel Plough)

01

02

03

00

01

01

00

01

02

03

01

01

00

8hr LEOdBfA)

89.3

89.3

89.3

86.3

86.4

87.9

91.0

91.0

90.9

90.6

90.1

91.5

91.9

OG's

F329

F316

F340/F353/F405/F419F425/F450

F437

F471/F491/F498/F503F508/F513/F518/F523F528/F533/F537/F542

F479

F465

F377

F387/F400/F440/F477

F382

F488

F535

F441

N28 Machine operator &(Gle i thobel Plough)

00 95.8 F443


NoiseGroup

N29

N30

N31

N32

N33

N34

Travel 8hr LEQDescription Sub-Grouo dB(A)

T/G Face End Prep.(Gleithobel Plough)

Coal Fillers(Belt Faces)

Shotfirers(Handfilled Faces)

Borers(Handfilled Faces)

Cutter operators/Meco Moore operators

Back Shift Prep.(Handfilled Faces)

00

01

02

03

02

03

03

01

02

03

01

02

03

91.8

84.6

85.1

85.6

91.3

90.7

94.5

91.1

90.9

90.9

89.9

89.5

89.5

OG's

F444

F55/F56/F63/F80

F7/F8/F9F10/F12/F42

F1/F2/F3/F4/F5/F6F11/F68/F70/F74/F97

F14

F15/F43

F22/F87

F57/F58/F64/F83F100

F28/F29/F48/F49

F23/F24/F25/F26/F27F30/F61/F77/F94F101/F106/F172

F59/F60/F62/F65/F66F67/F82/F102/F195

F33/F38/F39/F50/F51F52/F53

F31/F32/F34/F35/F36F37/F69/F72/F76F103/F173



Travel 8hr LEQSub-Group dB(A) OG's

N35 Belt Attendants 01

03

87.4 E17/E18/E20/E21/E44E45/E46

87.9 F40

N36 Face officials/Steel checkersLinesmen

03 89.5 E6/E34/E50/F54

N37 Coal Fillers(Undercut,Belt Faces)

03 85.6 F71

N38 Development

N40 L/G Stablemen(Handfilled,Panzer Faces)

02 89.1 E25/E26/E27/E28/E29E30/E35/E37/E48/E56E57/E58/E59/E50

03 89.4 F78

N39 Colliers(Panzer Faces)

01

03

85.9

86.5

F96/F194/F204

F79/F95/F107/F168

03 89.7 F92/F104

N41 T/G Stablemen(Handfilled,Panzer Faces)

03 88.8 F93/F105/F178/F179F180/F181

N42 YARMAK Face Team 00 91.4 F365


NoiseGroup

N43

N44

N45

N46

N47

N48

N49

N50

N51

N52

Description

Haulage Workers

Repairs, BackRip Salvage

Craftsmen (Out bye)

Loco Drivers

Officials (Outbye)

TravelSub-Group

00

02

02

01 .

03

01

Pitbottom Onsetters 00

Surface Screens

Surface C.P.P.

Surface General

Surface Workshop

00

00

00

00

8hr LEQdBCAl

87.4

85.3

91.7

89.8

93.9

86.3

90.3

96.0

88.5

90.8

91.1

OG's

E3

E1/E2/E4/E5/E14/E23E38/E39

E7/E8/E9/E10/E11E12/E36/E40/E41/E47

E16/E31/E52/E55

E32

E51

E15/E49

S1/S4

S2/S5/S9/S10

S3/S6/S7/S8/S10

Sll

APPENDIX 3

Hearing Levels

APPENDIX 3

TABLE 1

Hearing levels (best ear), by age and frequency, for 665 subjects

Key to table: mean (sd)median

Aee (years)Frequency(kHz) 2̂50.25 2

20.5 0

01 -3

-52 -3

-53 0

04 -0

-46 9

88 4

5

.6(6.0)

.0

.5(6.2)

.0

.0(5.0)

.0

.0(5.4)

.0

.5(6.5)

.0

.2(7.7)

.0

.4(9.6)

.0

.9(8.6)

.0

3̂02.7( 62.0-0.1( 6-1.0-2.4( 5-5.0-0.8( 7-4.02.2( 70.02.6( 80.010.4(1210.06.0(124.0

.4)

.8)

.6)

.1)

.4)

.6)

-6)

.1)

3̂52.0( 5.5)1.00.1( 6.7)-0.5-1.2( 6.6)-3.5-1.2( 6.4)-3.03.5( 6.5)3.04.0( 9.9)3.013.0(10.0)14.09.3(12.5)8.0

4̂04.6( 6.9)5.02.7( 7.9)2.01.4( 7.7)0.01.7( 9.0)0.06.9(10.9)5.07.9(10.2)7.017.5(12.6)15.013.6(12.4)10.0

4̂55.5( 7.5)5.04.1( 9.4)2.02.5( 9.0)0.02.3( 9.9)0.016.2(15.4)6.013.7(14.4)10.020.6(14.4)19.014.5(15.0)12.0

5̂05.8( 7.6)5.03.7( 8.8)2.02.0( 8.2)0.05.6(11.5)3.017. 4( 9.3)14.021.6(15.7)19.029.8(17.0)25.025.1(18.7)20.0

5̂56.8( 65.04.2( 55.03.6( 75.08.9(1110.042.0(3115.020.8(1221.030.7(1535.021.1(2115.0

.9)

.3)

.1)

.7)

.1)

.1)

.3)

.1)

>5520.0(1220.012.5(1012.57.5( 37.517.0(1817.0

42.059.0(1459.057.0(3257.071.0(2671.0

.7)

.6)

.5)

.4)

.1)

-5)

. )

APPENDIX 3

TABLES 2-9

Mean hearing levels (average of both ears)for 197 men, by age and NIL

Table 2- 0.25 kHz

Age (years) -96

-30 4.5

-40

>40

All 4.5

-98

8.1

8.5

-

8.1

NIL-100

4.3

1.4

-

3.7

(dB)-102

7.9

5.2

1.0

5.5

-104

3.5

5.7

8.0

6.9

>104

-

6.9

8.5

8.2

All

5.9

5.2

8.1

6.2

Table 3-0.5 kHz

Age (years) -96

-30 2.9

-40

>40

All 2.9

-98

5.6

6.8

-

5.6

NIL-100

2.4

-0.2

-

1.8

(dB)-102

2.2

5.1

-5.0

4.4

-104

2.5

3.5

7.1

5.4

>104

-

4.7

6.0

5.8

All

3.6

4.0

6.4

4.5

Table 4- 1 kHz

Age (years)

-30

-40

>40

All

NIL (dB)-96 -98 -100 -102

-0.1 2.3 -0.2 1.7

1.0 -0.5 3.3

0.5

-0.1 2.2 -0.3 3.0

-104

0.3

1.8

6.6

4.4

>104

-

2.6

6.5

5.8

All

0.8

2.3

6.4

2.7

Table 5- 2 kHz

Age (years')

-30

-40

>40

All

NIL (dB)-96 -98 -100 -102

-0.3 2.5 1.8 6.8

1.3 -1.6 2.0

-0.5

-0.3 2.4 1.0 2.6

-104

1.8

2.6

8.0

5.6

>104

-

4.2

10.3

9.3

All

1.7

1.9

8.9

3.6

Table 6 - 3 kHz

Age (years) -96

-30 3.1

-40

>40

All 3.1

-98

7.6

2.5

-

7.3

NIL (dB)-100 -102

5.2 12.5

4.4 8.1

3.0

5.0 8.6

-104

8.3

8.3

20.1

14.9

>104

-

11.4

23.2

21.1

All

6.0

7.8

21.2

10.5

Table 7 - 4 kHz

Age (years) -96

-30 1.8

-40

>40

All 1.8

-98

6.4

5.0

-

6.3

NIL CdB)-100 -102

4.5 11.4

6.0 9.6

10.0

4.8 9.9

-104

6.0

10.5

23.1

17.4

>104

-

10.7

27.3

24.3

All

4.8

9.4

24.7

11.4

Table 8 - 6 kHz

Age (years)

-30

-40

>40

All

-96 -98

13.6 18.4

20.0

-

13.6 18.5

NIL-100

15.3

16.3

-

15.5

CdB)-102

19.3

18.7

20.5

18.9

-104

18.8

18.2

32.4

26.2

>104

-

18.7

33.9

31.2

All

16.2

18.3

32.8

21.2

Table 9 - 8 kHz

Age (vears)

-30

-40

>40

All

-96 -98

8.8 12.7

14.5

-

8.8 12.8

NIL-100

9.8

12.8

-

10.5

CdB)-102

11.9

13.6

41.0

14.1

-104

13.5

20.3

24.4

22.3

>104

-

15.4

29.3

26.8

All

10.7

15.7

26.9

16.5

APPENDIX 4

TABLE 1

Expected median hearing levels (better ear) of malesby frequency and age, as published in ISO/DIS 1999 (1985)

(a) - age effect only;(b) - age effect plus noise Leq = 85 dB(A) ;(c) - age effect plus noise Leq = 90 dB(A)

Frequency(kHz)

(a) 0.512346

(b) 0.512346

(c) 0.512346

30

70291018

703121522

704162024

40

834131724

835172226

838222830

Age (years)50

1058192631

1059223033

10513283742

60

12610303645

12612344248

12615294752

APPENDIX 4

Expected median hearing levels

HEAD OFFICE:

Research Avenue North,Riccarton,Edinburgh, EH14 4AP, United KingdomTelephone: +44 (0)870 850 5131Facsimile: +44 (0)870 850 5132

Email: [email protected]

Tapton Park Innovation Centre,Brimington Road, Tapton,Chesterfield, Derbyshire, S41 0TZ, United KingdomTelephone: +44 (0)1246 557866Facsimile: +44 (0)1246 551212

Research House Business Centre,Fraser Road, Perivale, Middlesex, UB6 7AQ,United KingdomTelephone: +44 (0)208 537 3491/2Facsimile: +44 (0)208 537 3493

Brookside Business Park, Cold Meece, Stone, Staffs, ST15 0RZ,United KingdomTelephone: +44 (0)1785 764810Facsimile: +44 (0)1785 764811

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