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NOTE: This is a controlled document within the document control system. If revised, it must be marked SUPERSEDED and returned to the Vipac QA Representative. This document contains commercial, conceptual and engineering information that is proprietary to Vipac Engineers & Scientists Ltd. We specifically state that inclusion of this information does not grant the Client any license to use the information without Vipac’s written permission. We further require that the information not be divulged to a third party without our written consent.
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EXECUTIVE SUMMARY
Vipac was retained by Stratford Coal Pty Ltd to conduct an Environmental Noise Compliance Assessment (December 2015) in the rural environment surrounding the Stratford Coal mining operations as part of an on-going quarterly noise-monitoring program for Stratford Coal Pty Ltd.
The survey was requested by SCPL to ascertain the compliance of noise emissions generated from the operations of the mine with licence and consent conditions.
The following tables provide a summary of the noise impacts associated with Stratford Mine operations on all landowners that currently surround the coal-mining lease, monitored during the December 2015Environmental Compliance Assessment.
The Stratford Mine noise emissions were found to be compliant with the day, evening and night-time noise criterion at all residences on privately owned.
The measured contribution of mine noise emissions at most locations (based on the operator attended monitored LAeq noise levels) generally agrees with the corresponding predicted noise levels determined from the noise model. However some discrepancies were noted in the results, which are considered most likely to be attributed to the masking effect of other noise sources in the vicinity of the noise measurements such as passing traffic or wildlife noise.
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Stratford Mine Intrusive Noise (LA1 (1-minute)) – Night Monitoring Period 1 and 2
LocationSound Pressure Level6
dB LA1 (1-minute)
Noise Criteria
dB LA1 (1-minute)
Excursion
dB(A)
Atkins 27
45
0Hall 30 0
Lowrey 29 0Pryce Jones 35 0
Van Der Drift2 Nil 0All label notes are defined on pg6 of this report.
The intrusive noise impact emanating from Stratford mine was below 45dBLA1 (1-minute) at all of the noise sensitive receivers, as outlined in the table above.
These noise sensitive receivers are chosen to represent the nearest sensitive receptors surrounding the mine. Noise sensitive receptors located further from the mine site would be expected to experience reduced noise emission levels from the Stratford mine operations due to distance attenuation.
Assessment of Compliance
It is Vipac’s opinion that the Stratford Mine noise emissions were compliant with the Mine’s licence and Conditions of Consent at all residences on privately owned land during the December 2015 noise surveys taking into considerations the conditions outlined in Section 5.
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1 INTRODUCTION
Vipac Engineers and Scientists Ltd (Vipac) were commissioned by Stratford Coal Pty Ltd (SCPL) - Stratford Mine to undertake an Environmental Noise Compliance Assessment (December 2015) in the suburban and rural surroundings of the coal mining lease.
The purpose of this assessment was to conduct an environmental noise survey of the Stratford Mine operations and to determine the impact on the local community in accordance with the Noise Consent & Management Plan dated 15th May 2006 and SCPL development consent (McoA) Schedule 3, 26th November 2010.
A glossary of common acoustic terms and definitions is provided below in Table 1 as an aid to understanding this report.
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2 TABLE REFERENCES
The tables presented in this report include references with regard to individual properties/monitoring locations, where noise levels are assessed, either by way of attended noise surveys or by representation in the noise prediction model. This includes Table 3 in Section 3.3 below, Tables 8 – 10 in Section 6.1, Tables 11 – 14 in Section 6.6, Tables 15 – 17 in Section 7.1 and Table 18 in Section 7.2 of this report. The references associated with each of the footnotes in the tables referred to above are outlined as follows:
1. Nil indicates that there was no measurable mine noise.
2. Owned by Stratford Coal Pty Ltd.
3. Land Subject to acquisition upon request.
4. Alternate Location to R. Bagnall, as owner does not permit monitoring on his property
5. Wind speed was checked at each location during attended noise surveys at the monitoring positions.
3 METHODOLOGY
Ambient noise level measurements were conducted in accordance with the requirements of the Environmental Protection Authority (EPA) NSW Industrial Noise Policy (INP) and as detailed in Australian Standard AS1055-1997, “Acoustics - Description and Measurement of Environmental Noise”.
Environmental noise data loggers were positioned at monitoring locations (i.e. Hall, Lowrey, Van der Drift (former), Atkins (AGL), Ellis (former), Clarke Gates and the Mine (Weather Station) to measure ambient noise levels for a seventy-two hour survey period. Data from the SCPL Real Time Noise Monitor was utilised for the unattended survey at the Pryce Jones monitoring location. The Clarke Gates monitoring location was utilised as the monitoring location approved by the EPA, R. Bagnall, could not be monitored at as the property owner does not permit monitoring on their property.
3.1 OPERATOR ATTENDED NOISE SURVEYS
Operator attended noise surveys consisted of a monitoring regime where noise level measurements were conducted at nominated locations at different times of day, evening and night periods. Details of the monitoring periods for the attended surveys are provided in Table 2.
Table 2: Time of Noise Measurement SurveysTime of Day Date
Day 14/12/2015 14:00 - 17:30
Evening 14/12/2015 19:30 - 21:30
Night 14/12/2015 22:00 - 23:30
The Mine noise contribution can be determined using the following methods: -
When the Mine noise emissions are continuous in nature, the contribution is determined by noting the instantaneous sound level meter reading when the Mine operations are clearly audible and dominate the measurement environment.
When the Mine noise emissions are transient or frequency specific the contribution is determined by analysing the time trace and frequency spectra recordings to remove extraneous noise source/s from the measurement environment.
Alternatively, the contribution from the Mine can be determined by noting the relative audibility of the operations/activities, at otherwise quiet times, compared with the background noise levels at the particular time.
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3.2 INSTRUMENTATIONS
3.2.1 ATTENDED MEASUREMENTS
Attended noise measurements were taken with two Brüel & Kjær (B&K) 2250 integrating sound level meters (SLM), fitted with a B&K 4189 ½-inch diameter Electret microphone fitted with a windshield. These instruments have performance characteristics within the requirements of Class 1 accuracy in accordance with AS 1259 and AS IEC 61672 and have the capability to measure steady, fluctuating, intermittent and/or impulsive sound, and to compute and display percentile noise levels for the measuring period.
During the attended surveys, the instruments were used to record a 1/3-octave time trace of each 15-minute measurement, enabling detailed analysis of the acoustic environment. An audio recording function was utilised to enable crosschecking of the sample data where required.
A Rion Sound Level Calibrator was used to calibrate all measuring equipment prior to measurement and checked at the conclusion of the surveys. The difference in the two measurements was found to be less than 0.5 dB. A list of the Instrumentation used during the surveys is provided in Appendix B.
3.2.2 UNATTENDED NOISE LOGGING
Continuous noise levels were measured using Larson Davis 824 & 870 noise loggers as well as a Duo 01dB noise logger. Noise loggers were programmed to accumulate environmental noise data continuously over sampling periods of fifteen minutes duration for the entire seventy-two hour survey period. The internal software of each logger is capable of calculating and storing the LAn Percentile Noise Levels for the chosen sampling period, which can later be retrieved for detailed analysis.
3.3 MONITORING LOCATIONS
Attended and unattended noise monitoring locations incorporated into this survey are listed in Table 3 and are presented graphically on the Noise Monitoring Points Location Map, provided in Appendix C.
Table 3: Monitoring Locations
Location AddressAttended Monitoring Frequency
Day Evening Night
Atkins Off Wenhams Cox Road, Stratford 1 1 1
Clarke Gates4 Wenhams Cox Road, Stratford 1 1 -
Hall Upper Avon Road 1 1 1
Lowrey Off Crowthers Road Stratford 1 1 1
Pryce Jones The Bucketts Way, Craven 1 1 1
Ellis2,3 Off Wenhams Cox Road, Stratford 1 1 -
Van der Drift2 Wood Street, Stratford 1 1 1
Weather Station Stratford Coal Mine 1 1 1
Only one round of night surveys were conducted during this survey, as the coal handling processing plant was not operating on the second night (15/12/2015) or the third night (16/12/2015) of the survey.
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3.4 MONITORING WEATHER
Weather data during the survey period was obtained from the Stratford Operations weather station located on the mine access road adjacent to the rail loop.
The weather station is configured to continuously record meteorological parameters such as temperature, wind speed, wind direction, sigma-theta, and rainfall. Logged data from the weather station corresponding with the survey period is presented in Appendix D numerically as supplied by the Mine and graphically as a wind rose and wind speed chart.
4 CRITERIA
The following Tables of Criteria have been provided by Stratford Operations and are extracted from the Noise Consent & Management Plan and SCPL McoA Schedule 3.
As stated in McoA Schedule 3 Condition 1:
“Upon receiving a written request for acquisition from an owner of the land listed in Table 1 (reproduced in Table 4 of this report), the Applicant shall acquire the land in accordance with the procedure in Conditions 5-6 of Schedule 4.”
Table 4: Land Subject to acquisition upon requestLocation/Landowner
29-Ward31-Isaac
32-McIntosh33-Battaglini
40- Blanch41-Devereaux
Cr1- Wood
Noise generated by the development should not exceed the criteria outlined in Table 5.
Table 5: Noise Criteria dB(A)
LocationDay
LAeq (15 minute)
EveningLAeq (15 minute)
Night
LAeq (15 minute) LA1 (1 minute)
Craven Village
39 - Standen
42 - D Blanch
36 - Wallace
34 - Hall
25 - Thompson
298 - Yates
291 - Stackman
All other privately owned Land
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
40
40
40
37
36
36
36
36
35
45
45
45
45
45
45
45
45
45
Notes for Table 4:The noise emission limits identified in the above table apply under meteorological conditions of: Wind speeds of up to 3m/s at 10-metres above ground level; or Temperature inversion condition of up to 3C/100m
The noise levels presented in Table 6 establish the acquisition criteria applicable at any residence on privately owned land or on more than 25 per cent of any privately-owned land, with regard to any property where the owner submits a written request for acquisition by SCPL.
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Table 6: Table of Criteria – Noise Acquisition Limits
LocationDay
LAeq (15 minute)
EveningLAeq (15 minute)
NightLAeq (15 minute)
Stratford Village 42 41 40
Craven Village 42 41 40
All other Privately-owned land 40 40 40
Where the results show the noise generated by Stratford Operations is greater than, or equal to, LAeq(15-minute)
38dB(A) at night, additional noise mitigation measures are to be investigated in the form of architectural improvements to landowner’s dwellings.
Table 7 lists the criteria when additional noise mitigation measures are to be considered.
Table 7: Table of Criteria – Additional Noise Mitigation Measures
Landowner Night LAeq (15 minute)
Acquisition Zone 38
All other privately-owned land outside the acquisition zone 38
5 TEMPERATURE INVERSION CONDITIONS
Typically at SCPL, temperature inversion strength and occurrence is determined by utilizing the inversion tower data provided by the Stratford Mine and calculating the lapse rate based on Pasquill Stability Categories.
This section graphically presents calculated temperature inversion results for the survey period. A comparison against predicted inversion measurements is presented in Appendix D of this report.
Figure 1 below presents the calculated lapse rate from the measurement data collected by the inversion towers and indicates that there is a high occurrence of moderate to strong inversion occurrence at the beginning of the survey with the inversion strength weakening later in the night periods. Due to the high occurrence of moderate to strong temperature inversions, it is likely to give rise to noise enhancement during the early stages of the survey period, however toward the end of the survey period there is a decreased chance of noise enhancements due to the presence of the weak inversion conditions.
The times at which each of the compliance surveys were conducted are highlighted in yellow for ease of presentation.
The results of the attended surveys are presented in the following sections. Each measurement is presented in the form of a 15-minute time-trace along with relevant noise descriptors for the environment. The description of audible sounds, as noted during the measurement, has been matched to the noise data.
A low-pass frequency filter at 1.25 kHz has been presented along-side the broadband 1-second Leq trace to assist with the determination of contribution from low-frequency noise sources. These lower frequency noises can include rail movement, road traffic, aeroplanes, farm machinery, mine hum/coal handling and processing plant (CHPP), mine mobile plant engine/exhaust and others. The filter effectively removes higher frequency noises such as birds, insects, frogs and other extraneous noises.
The measured overall ambient noise levels include contributions from all noise sources including birds, insects, wind, road traffic, domestic noise, machinery, farm animals and the Stratford Operations. A second filter (yellow colour band in the graphs) effectively removes extraneous noise sources from the measurement environment.
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6.1 PREVAILING WEATHER CONDITIONSThe weather conditions at the time of each operator-attended noise measurement as obtained from the Stratford weather station and observations of the operator (cloud cover) are presented in the following tables.
Table 8: Prevailing Weather Conditions - Day Survey (14th December 2015)
Location Start Time (hrs) Temp (C) Cloud Cover (okta) Wind Speed 5 (ms-1) Wind Dir.
Location Start Time (hrs) Temp (C) Cloud Cover (okta) Wind Speed5 (ms-1) Wind Dir.
Pryce Jones 19:44 25.5 3 0.7 E
Hall 19:43 25.5 1 0.7 E
Lowrey 21:06 24.8 0 2.1 NE
Van Der Drift2 20:41 24.4 0 1.3 E
Atkins 20:40 24.4 0 1.3 E
Ellis 2,3 20:14 25.5 0 0.6 N
Clarke Gates4 20:16 25.5 3 0.5 N
Ref: Weather Station 21:28 23.6 0 0 -
Table 10: Prevailing Weather Conditions – Night Survey 1 (14th December 2015)
LocationStart
Time(hrs) Temp(C)Cloud Cover
(okta)Wind Speed
5
(ms-1)Wind Dir. Stability Class
Pryce Jones 22:00 23.1 0 0 - E
Hall 22:00 23.1 0 0.2 E E
Lowrey 22:46 21.0 0 0.6 NE E
Van Der Drift2 23:12 20.0 0 0 - E
Atkins 23:11 20.0 0 0.2 NE E
Ref: Weather Station 22:24 21.6 0 1.4 NNW E
6.2 MINE PRODUCTION & OPERATIONS
Due to the mine currently being in care and maintenance the only operations during the attended day, evening and night periods were that of the CHPP, CHPP dozer and loader. The coal handling processing plant however was only operating during the first night of the survey period on 14/12/2015 and was not operating during the second or third night of the survey on the 15/12/2015 and 16/12/2015.
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6.3.1 ANALYSIS – DAY SURVEY
The Mine noise emissions at the reference site (Stratford Weather Station) measured 46dBLAeq during typical operations on the Mine lease. Audible noise sources that contributed to this result consisted of the continual hum of coal processing plant operations and mobile plant operations.
At noise sensitive receivers extraneous noise sources (i.e. frequent road traffic movements, continuous sounds from birds, insects, dogs and passing rail traffic) were removed from the overall noise measurement, which resulted in the Mine noise contribution being determined at each location.
Prevailing weather conditions at each monitoring location were characterised by partially cloudy skies with light winds blowing from a north westerly to north easterly direction as per the observations of Vipac engineers on site on the 14th December 2015. Weather Data from the SCPL Weather Station is provided in Appendix Dof this report.
A summary of the Stratford Operations noise emissions, LAeq 15-minute measured at the nominated monitoring locations, under the prevailing weather conditions during the day period are presented below.
Atkins - Nil, Insects, Birds, Traffic and Aircraft
Clarke Gates - Nil, Insects, Birds and Aircraft Noise
Ellis – Nil, Insects, Birds and Aircraft Noise
Hall – Nil, Birds & Insects, Traffic Noise
Lowrey - Nil, Birds & Insects, Traffic Noise
Pryce Jones – Nil, Birds & Insects, Traffic Noise
Van Der Drift – Nil, Birds & Insects, Traffic Noise
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6.4.1 ANALYSIS – EVENING SURVEY
The Mine noise emissions at the reference site (Stratford Weather Station) measured 50dBLAeq during typical operations on the Mine lease. Audible noise sources that contributed to this result consisted of the continual hum of the CHPP and mobile plant operations.
At noise sensitive receivers extraneous noise sources (i.e. frequent road traffic movements, continuous sounds from birds, insects, dogs and passing rail traffic) were removed from the overall noise measurement, which resulted in the Mine noise contribution being determined at each location.
Prevailing weather conditions were characterised by predominantly clear skies with still to light-easterly to north easterly wind conditions, on the 14th December 2015. Weather Data from the SCPL Weather Station is provided in Appendix D of this report. Sigma-theta data indicated weak temperature inversion throughout the evening survey period.
A summary of the Stratford Operations noise emissions, LAeq 15-minute measured at the nominated monitoring locations, under the prevailing weather conditions during the evening period are presented below.
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6.5.1 ANALYSIS – NIGHT SURVEY 1
The Mine noise emissions at the reference site (Stratford Weather Station) measured 45dBLAeq during typical operations on the Mine lease. Audible noise sources that contributed to this result consisted of the continual hum of coal processing plant operations and operation of the dozer on the stockpile.
At noise sensitive receivers extraneous noise sources (i.e. road traffic movements, sounds from birds, insects, dogs and passing rail traffic) were removed from the overall noise measurement, which resulted in the Mine noise contribution being determined at each location.
Prevailing weather conditions were characterised by predominantly clear skies with still to light north easterlywind conditions, as per observations of Vipac Engineers on the 14th December 2015 at each monitoring location. Weather Data from the SCPL Weather Station is provided in Appendix D of this report. Sigma-theta data indicated weak temperature inversion throughout the first night survey period
A summary of the Stratford Operations noise emissions, LAeq 15-minute measured at the nominated monitoring locations, under the prevailing weather conditions during the first night period are presented below.
Atkins -20dB(A), Mobile Plant
Hall - 27dB(A), Mobile Plant
Lowrey -26dB(A), CHPP Hum and Dozer Engine
Pryce Jones – 32dB(A), CHPP Hum,
Van Der Drift – Nil, Insects, Dog Barking and Traffic Noise
The Stratford Operations LA1(1 minute) noise contributions for the first night period are presented below as follows:
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6.6 ATTENDED NOISE COMPLIANCE ASSESSMENT
Table 13 – Table 16 below show the Stratford Mine LAeq (15-minute) and LA1 (1-minute) noise impact on the nominated sensitive receivers during the day, evening and night attended noise-monitoring periods. The Stratford Mine noise contribution received at each property is compared to the respective noise criterion outlined in Section 4of this report.
Table 11: Stratford Mine Noise Contribution – Day Monitoring Period
LocationSound Pressure Level6
dB LAeq (15-minute)
Noise Criteria
dBLAeq (15-minute)
Excursion
dB(A)
Atkins Nil
35
0Clarke Gates4 Nil 0
Ellis2,3 Nil 0
Hall Nil 0
Lowrey Nil 0
Pryce Jones Nil 0
Van Der Drift2 Nil 0
Table 12: Stratford Mine Noise Contribution – Evening Monitoring Period
LocationSound Pressure Level6
dBLAeq (15-minute)
Noise Criteria
dBLAeq (15-minute)
Excursion
dB(A)
Atkins Nil
35
0Clarke Gates4 Nil 0
Ellis2,3 Nil 0Hall Nil 0
Lowrey 30 0Pryce Jones 27 0
Van Der Drift2 29 0
Table 13: Stratford Mine Noise Contribution – Night Monitoring Period 1
LocationSound Pressure Level6
dBLAeq (15-minute)
Noise Criteria
dBLAeq (15-minute)
Excursion
dB(A)
Atkins 20
35
0Hall 27 0
Lowrey 26 0Pryce Jones 32 0
Van Der Drift2 Nil 0
Table 14: Stratford Mine Intrusive Noise (LA1 (1-minute)) – Night Monitoring Period 1
LocationSound Pressure Level6
dB LA1 (1-minute)
Noise Criteria
dB LA1 (1-minute)
Excursion
dB(A)
Atkins 27
45
0Hall 30 0
Lowrey 29 0Pryce Jones 35 0
Van Der Drift2 Nil 0
The Stratford Mine noise emissions were found to be below the day, evening and night-time noise criterion at all residences on privately owned land for the December 2015 Noise Compliance Survey.
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7 UNATTENDED CONTINUOUS NOISE LOGGING
Ambient noise levels for unattended continuous noise logging do not necessarily reflect the exact noise contribution from the Stratford operations. It quantifies the overall noise level at a given location from all noise sources. The loggers calculate the statistical noise indices and do not record the actual sources. Other results are predicted based upon attended measurements conducted during the survey and comments on accuracy are provided.
7.1 SUMMARY OF UNATTENDED NOISE MEASUREMENTS
A summary of the unattended noise logger data following the removal of weather affected (e.g. high wind speeds and/or rain) is presented in Table 15 – Table 19 for the period 14th -17th December 2015.
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7.2 NOISE MODEL PREDICTION
To determine the noise contribution from Stratford Mine it is appropriate to eliminate any ambient noise level data, which correlates with localised noise sources (e.g. insects, dogs, traffic etc.). This process involves discarding the noise contribution from extraneous sources such as insects, dogs and traffic etc., which can be continuous or intermittent in nature.
The mine contributed noise emissions from mining and process operations for each monitoring location were calculated by using an environmental noise model of the total CHPP and mining operations. The model inputs incorporate:
Current sound power levels of mobile plant and fixed machinery associated within the Mine;
Prevailing meteorological conditions over the actual 72-hour monitoring period;
Operator-Attended noise monitoring results from the time of day.
The current mine production, operations and weather data were supplied by Stratford Operations as set out in Table 12 and in Appendix D. Calculated day, evening and night contributed noise emissions from the Stratford Mine to each owner/tenant monitoring location are presented in Table 20.
Noise criteria for this survey are applicable for all attended noise measurements notwithstanding meteorological conditions during the course of survey.
Comparing the predicted noise impact with the time of day (noise) criterion for each residence indicates no excursions of the noise consent conditions surrounding the Stratford Operations.
Table 18: Environmental Noise Levels – December 2015
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8 DISCUSSION AND CONCLUSION
Vipac was retained to conduct an Environmental Noise Compliance Assessment (December 2015) in the rural environment surrounding the Stratford Coal mining operations as part of an on-going quarterly noise-monitoring program for Stratford Coal Pty Ltd.
The survey was requested by SCPL to ascertain the compliance of noise emissions generated from the operations of the mine with licence and consent conditions.
The Stratford Mine noise emissions were found to be compliant with the day, evening and night-time noise criterion at all residences on privately owned land. The measured contribution of mine noise emissions at most locations (based on the operator attended monitored LAeq noise levels) generally agrees with the corresponding predicted noise levels determined from the noise model. However some discrepancies were noted in the results, which are considered most likely to be attributed to the masking effect of other noise sources in the vicinity of the noise measurements such as passing traffic or wildlife noise.
8.1 ASSESSMENT OF COMPLIANCE
It is Vipac’s opinion that the Stratford Mine noise emissions were compliant with the Mine’s licence and Conditions of Consent at all residences on privately owned land during the December 2015 noise surveys under the conditions outlined in the Section 6 of this report.
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GLOSSARY OF TERMSAppendix A:
A-Weighted Decibel (dB(A)) – The overall level of a sound is usually expressed as dB(A), instead of dB. The
sound is measured using an A-weighted filter, which is incorporated into the sound level meter. The filter is used to approximate the response of the human ear. It reduces the significance of lower frequencies and very high frequencies, thereby increasing the importance of mid-frequencies (500Hz to 4kHz).
A change of 1 to 2dB(A) is difficult to detect, whilst a change of 3 to 5dB(A) corresponds to a small but noticeable change. A 10dB(A) change approximates to a doubling or halving in apparent loudness.
LAeq is the time averaged A-weighted sound pressure level for the interval, as defined in AS1055.1. It is generally described as the equivalent continuous A-weighted sound pressure level that has the same mean square pressure level as a sound that varies overtime. It can be considered as the average sound pressure level over the measurement period.
LAn is the sound level, which, for a specified time interval, in relation to an investigation of a noise, means the A-weighted sound pressure level that is equalled or exceeded for n% of the interval. Commonly used percentages are 1, 10, 90 & 99%.
Noise Logger A Noise Logger is used at unattended survey sites to continuously measure and record the noise level at that location.
Octave frequency bands allow a representation of the spectrum associated with a particular noise. They are an octave wide, meaning that the highest frequency in the band is just twice the lowest frequency, with all intermediate frequencies included and all other frequencies excluded. Each octave band is described by its centre frequency.
Sound Pressure Level (Lp) – Sound or noise is the sensation produced at the ear by very small fluctuations in atmospheric pressure. The human ear responds to changes in sound pressure over a very wide range (from 20 micro Pascals to 60 Pascals). A scale that compresses this range to a more manageable size and that is best matched to subjective response is the logarithmic scale, rather than a linear scale.
Sound Pressure Level (Lp) is defined as:
In the above equation, p is the sound pressure fluctuation (above or below atmospheric pressure), and pref is 20 micro Pascals (2 x 10-5 Pa), the approximate threshold of hearing. To avoid a scale which is too compressed, a factor of 10 is included, giving rise to the decibel, or dB for short.
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