An ear is for listening, and for the lucky few, listeningto music is their job. But an ear is for much more—loseyour hearing, and besides not hearing music, you loseyour connection with other people. Hearing is the sensemost related to learning and communication, and is thesense that connects you to ideas and other people. HelenKeller, who lost both her sight and hearing at a youngage, said that hearing loss was the greater affliction forthis reason.
To professionals in the music industry, their hearingis their livelihood. To be able to hear well is the basisfor sound work. Protecting your hearing will determinewhether you are still working in the industry when youare 64, or even whether you can still enjoy music, and itwill determine whether you will hear your spouse andgrandchildren then, too.
47.1.1 What Does Hearing Damage Sound Like?
Hearing loss is the most common preventable workplaceinjury. Ten million Americans have noise-induced hear-ing loss. Ears can be easily damaged, resulting in partialor complete deafness or persistent ringing in the ears.
Hearing loss isn’t necessarily quiet. It can be amaddening, aggravating buzz or ringing in the ear,called tinnitus. Or it may result in a loss of hearingability, the ability to hear softer sounds at a particularfrequency. The threshold of hearing, the softest soundsthat are audible for each frequency, increases as hearingloss progresses. Changes in this threshold can either bea temporary threshold shift (TTS) or a permanentthreshold shift (PTS). Often these changes occur in thehigher frequencies of 3000 to 6000 Hz, with a notch orsignificant reduction in hearing ability often around4000 Hz.
A single exposure to short-duration, extreme loudnoise or repeated and prolonged exposure to loud noisesare the two most common causes of hearing loss. Exam-ples of the first might be exposure to noise fromdischarging firearms, while the second might be thecumulative effects of working in a noisy environmentsuch as manufacturing or in loud concert venues. Someantibiotics, drugs, and chemicals can also cause perma-nent injury.
Hearing damage isn’t the only health effect of noise.Workers in noisy workplaces have shown a higher like-lihood of heart disease and heart attacks. Numerousother stress-related effects have been documented,including studies that have shown that women in noisyenvironments tend to gain weight.
47.2 How Loud Is Too Loud? OSHA, NIOSH, EPA, WHO
As in other industries, workers in the sound industry arecovered by the occupational noise exposure standardfound in the Code of Federal Regulations (29 CFR1910.95). Occupational Safety and Health (OSHA) reg-ulation requires that workers’ exposures not exceedthose in Table 47-1.
Noise levels are measured with a sound level meteror dosimeter (a sound level meter worn on theemployee) that can automatically determine the averagenoise level. Often, noise levels are represented in termsof a daily dose. For example, a person who was exposedto an average level of 90 dBA for four hours wouldhave received a 50% dose, or half of her allowableexposure.
Administrative controls—such as the boss saying,“Don’t work in noisy areas, or do so for only shorttimes,” and/or engineering controls—such as quietermachines—are required to limit exposure. Hearingprotection may also be used, although it is not thepreferred method. Moreover, the regulation requiresthat, for employees whose exposure may equal orexceed an 8-hour time-weighted average of 85 dB, theemployer shall develop and implement a monitoringprogram in which employees receive an annual hearingtest. The testing must be provided for free to theemployee. The employer is also required to provide aselection of hearing protectors and take other measuresto protect the worker.
Compliance by employers with the OSHA regula-tions, as well as enforcement of the regulation, is quitevariable, and often it is only in response to requestsfrom employees. It is quite possible that professionals inthe field have never had an employer-sponsored hearingtest, and are not participating in a hearing conservationprogram as required.
Unfortunately, OSHA’s regulations are among theleast protective of any developed nation’s hearingprotections standards. Scientists and OSHA itself haveknown for more than a quarter-century that between 20and 30% of the population exposed to OSHA-permittednoise levels over their lifetime will suffer substantialhearing loss, see Table 47-2. As a result, the NationalInstitute of Occupational Safety and Health (NIOSH), abranch of the Centers for Disease Control and Preven-tion (CDC), has recommended an 85 dB standard asshown in Table 47-3. Nevertheless, NIOSH recognizesthat approximately 10% of the population exposed to thelower recommended level will still develop hearing loss.
Table 47-3 compares the permissible or recom-mended daily exposure times for noises of variouslevels. The table is complicated but instructive. The firstthree columns represent the recommendations of theEnvironmental Protection Agency (EPA) and WorldHealth Organization (WHO) and starts with the recom-mendation that the 8-hour average of noise exposure notexceed 75 dBA. The time of exposure is reduced by halffor each 3 dBA that is added; a 4-hour exposure is78 dBA, and a 2-hour exposure is 81 dBA. This iscalled a 3 dB exchange rate, and is justified on the prin-ciple that a 3 dB increase is a doubling of the energyreceived by the ear, and therefore exposure time oughtto be cut in half. The EPA and WHO recommendationscan be thought of as safe exposure levels. The NIOSHrecommendations in the next three columns represent anincreased level of risk of hearing loss and are notprotective for approximately 10% of the population.NIOSH uses a 3 dB exchange rate, but the 8-hour expo-sure is 10 dB higher than EPA—that is, 85 dBA.Finally, the OSHA limits are in the last two columns.OSHA uses a 5 dB exchange rate, which results inmuch longer exposure times at higher noise levels, andthe 8-hour exposure is 90 dBA. Between 20 and 30% ofpeople exposed to OSHA-permitted levels will experi-ence significant hearing loss over a lifetime of expo-
Table 47-2. NIOSH’s 1997 Study of Estimating Excess Risk of Material Hearing ImpairmentAverage ExposureLevel–dBA
Risk of Hearing Loss Depending onthe Definition of Hearing Loss Used
90 (OSHA) 25–32%85 (NIOSH) 8–14%80 1–5%While 25–30% of the population will suffer substantial hearingloss at OSHA permitted levels, everyone would suffer some hear-ing damage.
Table 47-3. EPA, WHO, NIOSH, and OSHA Recom-mended Decibel Standards
sure. It is important to note that everyone exposed to theOSHA-permitted levels over their lifetime will experi-ence some hearing loss.
It is important to remember that each of these recom-mendations assumes that one is accounting for all of thenoise exposure for the day. Someone who is working ina noisy environment, then goes home and uses powertools or lawn equipment, is further increasing the riskand exposure.
The U.S. Environmental Protection Agency (EPA)and the World Health Organization (WHO) haverecommended a 75 dB limit, as shown in Table 47-3, asa safe exposure with minimal risk of hearing loss. TheWHO goes on to recommend that exposure such as at arock concert be limited to four times per year.
47.3 Indicators of Hearing Damage
There are several indicators of hearing damage. Sincethe damage is both often slow to manifest itself and pro-gressive, the most important indicators are the ones thatcan be identified before permanent hearing damage hasoccurred.
The first and most obvious indicator is exceeding theEPA and WHO safe noise levels. As noise 8 hours, riskof suffering hearing loss also increases.
Exceeding the safe levels by, for example, workingat OSHA-permitted noise levels doesn’t necessarilymean you will suffer substantial hearing loss; somepeople will suffer substantial loss, but everyone willsuffer some level of hearing damage. The problem isthat there is no way to know if you are in the onequarter to one third of the population who will suffersubstantial hearing loss at a 90 dBA level or the twothirds to thre quarters of the population who will loseless—at least, not until it is too late and the damage hasoccurred. Of course, by greatly exceeding OSHA limits,you can be assured that you will have significanthearing loss.
There are two types of temporary hearing damagethat are good indicators that permanent damage willoccur if exposure continues. The first is tinnitus, atemporary ringing in the ears following a loud orprolonged noise exposure. Work that induces tinnitus isclearly too loud, and steps should immediately be takento limit exposure in the future.
The second type of temporary damage that is auseful indicator of potential permanent damage is atemporary threshold shift (TTS). Temporary changes inthe threshold of hearing, the softest sounds that areaudible for each frequency, are a very good indicatorthat continued noise exposure could lead to permanent
hearing loss. Although ways to detect TTS withoutcostly equipment are now being developed, the subjec-tive experience of your hearing sounding different afternoise exposure currently provides the best indication ofproblems.
It is important to remember that the absence of eitherof these indicators does not mean you will not sufferhearing loss. The presence of either is a good indicationthat noise exposure is too great.
Regular hearing tests can’t detect changes in hearingbefore they become permanent, but if frequent enough,they can detect changes before they become severe. It isparticularly important, therefore, that people exposed toloud noises receive regular hearing tests.
Finally, there are often indicators that serious hearingdamage has occurred, such as difficulties understandingpeople in crowded, noisy situations (loud restaurants,for example), the need to say “What?” frequently, orasking people to repeat themselves. Often it is not theperson with the hearing loss, but rather others aroundhim or her, who are the first to recognize these problemsdue to the slow changes to hearing ability and denialthat often accompany them. While it is impossible toreverse hearing damage, hearing loss can be mitigatedsomewhat by the use of hearing aids, and furtherdamage can be prevented. It is important to rememberthat just because you have damaged your hearingdoesn’t mean you can’t still make it much worse.
47.4 Protecting Your Hearing
Protecting your hearing is reasonably straightforward:avoid exposure to loud sounds for extended periods oftime. This can be accomplished by either turning downthe volume or preventing the full energy of the soundfrom reaching your ears.
There are several strategies for protecting yourhearing if you believe or determine that your exposureexceeds safe levels. As Table 47-3 indicates, you canreduce the noise level or reduce the exposure time, orboth.
While reducing exposure time is straightforward it isnot always possible, in which case turning down thevolume by using quieter equipment, maintaining agreater distance from the noise source, using barriers ornoise-absorbing materials, or utilizing hearing protec-tion (either earplugs or over-the-ear muffs, or both) arerequired.
Typical earplugs or earmuffs are often criticized forchanging the sound and hindering communication.Hearing protection in general is far better at reducingnoise in the higher frequencies than the lower frequen-
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cies, so typical hearing protection significantly changesthe sound a wearer is hearing. Consonant sounds inspeech occur in the frequencies that are more greatlyattenuated by some hearing protectors.
There are, however, a number of hearing protectiondevices designed to reduce noise levels in all frequen-cies equally. Often referred to as musician’s earplugs,t he s e c a n c o m e i n i n e x p e n s i v e m o d e l s o rcustom-molded models. The advantage of a flat orlinear attenuation of noise across all frequencies is thatthe only change to the sound is a reduction in noiselevel.
47.4.1 Protecting Concert-Goers and Other Listeners
Ears are for listening, and when it comes to music, thereare often many ears listening to the music. They too,like music professionals, are at risk of hearing loss.Loud music is exciting; that is the physiology of loud. Itgives us a shot of adrenaline. Also, more neurons arefiring in our brain and our chest is resonating with thelow-frequency sounds.
When humans evolved, the world was much quieterthan it is today. Infrequent thunder was about it for loudnoise. Hearing evolved to be a very important sensewith respect to our survival, working 24/7 to keep usinformed about the changing conditions of our environ-ment. Noise wakes us up, because if it didn’t wake ourforebears up when trouble entered the camp, they mightnot live long enough to create descendants. Noise is animportant warning device—think of a child’s crying orscreaming. During most of human history, when it wasloud, trouble was involved. Physiologically, loud noisesgive us a shot of adrenaline, gearing us up to either fightor flee. Today, while neither fight nor flight is an appro-priate response to loud noise, we still receive that shotof adrenaline. This is the reason for the popularity ofloud movie soundtracks, loud exercise gyms, and loudmusic. It adds excitement and energy to activities. But itis also the reason for the stress-related effects of noise.
There is great incentive to turn it up, especially sincethe consequences are often not experienced until yearslater when the extent of hearing damage becomesapparent. People come to concert venues for excite-ment, not to be bored, and they come willingly; in fact,they pay to inflict whatever damage might be caused.Still, it is not a well-informed decision, and oftenminors are in the audience. But mostly, it isn’t neces-sary. The desired physiological responses occur at lowernoise levels. Moreover, it makes little sense for anindustry to degrade the experience of listening to music
in the future for whatever marginal gain comes fromturning it up a few more decibels now.
Fortunately, even small gestures to turn it down havenoticeable impacts. Because every 3 dB decrease halvesexposure, small decreases in sound pressure level canvastly increase public safety.
47.4.2 Protecting the Community
Noise can spill over from a venue into the community.The term noise has two very different meanings. Whendiscussing hearing loss, noise refers to a sound that isloud enough to risk hearing loss. In a community set-ting, noise is aural litter. It is audible trash. Noise is tothe soundscape as litter is to the landscape. When noisespills over into the community, it is the aural equivalentof throwing McDonald’s wrappers onto someone else’sproperty.
When noise reaches the community, often it has lostits higher-frequency content, as that is more easilyattenuated by buildings, barriers, and even the atmo-sphere. What is often left is the bass sound.
Solutions to community noise problems are asnumerous as the problems themselves, and usuallyrequire the expertise of architectural acousticians. Ingeneral, carefully aimed distributed speaker systems arebetter than large stacks for outdoor venues. Barriers canhelp, but not in all environmental conditions, and theireffectiveness tends to be limited to nearer neighbors.Moreover, barriers need to be well designed, with nogaps.
Indoor walls with higher sound transmission class(STC) ratings are better than ones with lower ratings.STC ratings, however, do not address low-frequencysounds that are most problematic in community noisesituations, so professional advice is important whenseeking to design better spaces or remedy problems.
Windows and doors are particularly problematic, aseven these small openings can negate the effects of verywell-soundproofed buildings. They also tend to be theweakest point, even when shut.
Sound absorption is useful for reducing transmis-sion through walls, but in general, decoupling the inte-rior and exterior so that the sound vibrations that hit theinterior wall do not cause the exterior wall to vibrateand reradiate the noise is more effective. There arenumerous products available to achieve both decouplingand sound absorption.
Often, however, employing these techniques is notan option for the sound engineer. In that case, control-ling sound pressure levels and low-frequency levels arethe best solution.
What’s the Ear For? How to Protect It 1637
47.5 Too Much of a Good Thing
In today’s world, noise represents one of the more seri-ous pollutants, Fig. 47-1. Some are the by-product ofour society such as lawn mowers, jackhammers, traffic,and public transportation.
We deliberately subject ourselves to a Pandora’s boxof sounds that threaten not only our hearing but ourgeneral health. Personal sources like MP3 players, carstereos, or home theaters are sources we can control, yetmany remain oblivious to their impact, Fig. 47-2. In thepublic domain clubs, churches, auditoriums, amphithe-aters, and stadiums are part of the myriad of potentialthreats to hearing health. From a nuisance to a serioushealth risk, these sources impact attendees, employees,and neighbors alike. As pointed out previously, levels of105 dBA for 1 hour or less may result in serious andpermanent hearing damage. Recent studies have shownother factors such as smoking, drugs of all types, andthat overall health appear to accelerate the process.
High sound levels are just part of the problem.Sound does not stop at the property line. Neighbors andneighborhoods are affected. Numerous studies have
shown persistent levels of noise affect sleeping patterns,even increase the potential for heart disease. Studies byJohns Hopkins have shown hospital noise impactspatients in the neonatal wards and other patients’recovery time.
Communities all over the world have enactedvarious forms of noise ordinances. Some address noisebased on the annoyance factor. Others specify noiselimits with sound pressure level (SPL), time of day, andday of the week regulations. The problem, noise(sound), is a transient event. Enforcement and compli-ance are often very difficult, especially when treated asan annoyance.
47.5.1 A Compliance and Enforcement Tool
There are various tools to monitor noise. One very use-ful tool is “the SLARM™ by ACO Pacific. The follow-ing will use the SLARM™ to explain the importance ofnoise-monitoring test gear. The SLARM™ tool wasdeveloped to meet the needs of the noise abatementmarket. The SLARM™ performs both compliance andenforcement roles, offering accurate measurement,alarm functions, and very important history.
For the business owner dealing with neighborhoodcomplaints, the SLARM™ provides a positive indica-tion of SPL limits—permitting employees to control thelevels or even turn off the sound. The History functionoffers a positive indication of compliance.
On the enforcement side, no longer does enforce-ment have to deal with finger-pointing complaints. Theynow may be addressed hours or days after the event andresolved. There is also the uniform effect. Police pull uparmed with a sound level meter (SLM) and the volumegoes down. Businesses now can demonstrate compli-ance. Yes—it is an oversimplification— but the conceptworks. Agreements are worked out. Peace and quietreturn to the neighborhood.
47.5.1.1 The SLARMSolution™
The SLARM™ (Sound Level Alarm and Monitor) is apackage of three basic subsystems in a single standalonedevice:
1. A sound level meter designed to meet or exceedType 1 specifications.
2. Programmable threshold detectors providing eitherSPL or Leq alarm indications.
3. Monitor—a data recorder storing SPL data, andLed values for about 3 weeks on a rolling basis, aswell as logging unique Alarm events, scheduled
Figure 47-1. Derivation of noise. Courtesy ACO Pacific.
Figure 47-2. Loud sounds from passing cars are oftenaggravating to passers by. Courtesy ACO Pacific.
The SLARM™ may operate standalone. A PC is notrequired for normal Alarm operation. The data is main-tained using flash and ferro-ram devices.
The SLARM™ provides USB and serial connec-tivity. It may be connected directly to a PC or viaoptional accessories directly to an Ethernet or radio linksuch as Bluetooth™.
PC operation is in conjunction with the includedSLARMSoft™ software package.
47.5.1.2 SLARMSoft™ Software Suite
SLARMWatch™. A package with password-protectedsetup, calibration, downloading, display, and clearing ofthe SLARM™’s SPL history. The history data may besaved and imported for later review and analysis,Fig. 47-3.
SLARMAnalysis™. Part of SLARMWatch™ providestools for the advanced user to review the SLARM™history files. SLARMWatch™ allows saving andstorage of this file for later review and analysis. SLAR-MAnalysis™ provides Leq, Dose and other calculationswith user parameters, Fig. 47-4.
SLARMScheduler™. Part of the SLARMWatch™package, allows 24/7 setting of the Alarm thresholds.This permits time of day and day of the week adjust-ments to meet the needs of the community, Fig. 47-5.
WinSLARM™. A display of SPL, Leqs, Range, andAlarm settings with digital, analog bar graph, and meterdisplays, as well as a Histogram window that provides a
25 second view of recent SPL on a continuous basis.The WinSlarm™ display may be sized permitting singleor multiple SLARM™s to be shown, Fig.47-6.
SLARMAlarm™. Opera te s independent ly f romSLARMWatch™. The package monitors SLARM™sproviding digital display of SPL and Leqs values whilealso offering SMS, text, and email messaging of Alarmevents via an Internet connection from the PC, Fig. 47-7.
SLARMNet™. The SLARM™ and the SLARM-Soft™ package allow multiple SLARM™s to be
Figure 47-3. SLARMWATCH™ History and Events andthree SLARM™ displays. Courtesy ACO Pacific.
Figure 47-5. SLARMScheduler™ Panel. Thresholds may beindividually set for each ALARM over a 24-hour, 7-dayperiod. Courtesy ACO Pacific.
What’s the Ear For? How to Protect It 1639
connected to a network providing real-time data withalarm indications to multiple locations.
47.5.1.3 SLARM™ Operation
The SLARM™ operates in the following manner,Fig. 47-8.
The Microphone and Microphone Preamplifier. T h e7052/4052 microphone and preamplifier are suppliedwith the SLARM™ system. The 7052 is a Type 1.5™
½ inch free-field measurement microphone featuring atitanium diaphragm. The microphone has a frequencyresponse from <5 Hz to 22 kHz and an output level of22 mV/Pa (–33 dBV/Pa). The 4052 preamplifier is pow-ered from 12 Vdc supplied by the SLARM™ and has aresponse <20 Hz to >100 kHz. Together they permitmeasurements approaching 20 dBA. The MK224 elec-tret capsule is available, offering 8 Hz to 20 kHzresponse, and 50 mV/Pa (–26 dBV/Pa) performanceproviding a lower noise floor. The diaphragm is quartzcoated nickel.
The Preamplifier (Gain Stage). A low noise gain stageis located after the microphone input. This stageperforms two tasks. The first limits the low-frequencyinput to just under 10 Hz. This reduces low-frequencyinterference from wind or doors slamming, things we donot hear due to the roll-off of our hearing below 20 Hz.The gain of this stage is controlled by the microcon-troller providing two 100 dB measurement ranges 20 to120 dB and 40 to 140 dBSPL. Most measurements areperformed with the 20 to 120 dBSPL ranges. Customranges to >170 dBSPL are available as options. Theoutput of the gain stage is supplied to three analog filterstages “A”, “C” and “Z” (Linear).
Analog A- and C-Weighted Filters. The gain stage isfed to the C-weighted filter. C-weighted filters have a 3dB response limit of 31.5 Hz to 8 kHz. C-weighted fil-ters are very useful when resolving issues with low fre-quencies found in music and industrial applications. Theoutput of the C-weighted filter is connected to both theanalog switch providing filter selection and the input ofthe A-weighted element of the filter system. Sound lev-els measured with the C-weighted filter are designated asdBC (dBSPL C weighted).
The A-weighted response is commonly found inindustrial and community noise ordinances. A weightingrolls off low-frequency sounds. Relative to 1 kHz, theroll-off is –19.4 dB at 100 Hz (a factor of 1:10) and–39.14 at 31.5 Hz (a factor of 1:100). The A responsesignificantly deemphasizes low-frequency sounds.Sound levels measured with the A-weighted filter aredesignated as dBA (dBSPL A weighted). The output ofthe A-weighted filter is sent to the analog switch.
Analog Z-Weighting (Linear) Filter. The Z designa-tion basically means the electrical output of the micro-phone is not weighted. The SLARM™ Z-weightingresponse is 2 Hz to >100 kHz. The response of thesystem is essentially defined by the response of themicrophone and preamp. Z weighting is useful wheremeasurements of frequency response are desired, or
Figure 47-6. WinSLARM™ display provides a real-time lookat SPL, Leq Thresholds, and recent events. Courtesy ACOPacific.
Figure 47-7. SLARMAlarm™ display with three SLARM™s.Note: ACOP2 has both USB and Ethernet (via a serialadaptor) connections. Courtesy ACO Pacific.
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where low or h igh f requencies are important .Remember the microphone response determines theresponse. Sound levels measured with the Z weightedfilter are designated as dBZ (dBSPL Z weighted).
Analog Switch. T h e o u t p u t s o f t h e A - , C - , a n dZ-weighted filters connect to the analog switch. Theswitch is controlled by the microcontroller. The selec-tion of the desired filter is done at setup using the utili-ties found in SLARMWatch™.
Selection of the filter as with the other SLARM™settings is password protected. Permission must beassigned to the user by the administrator before selec-tion is possible. This is essential to minimize the possi-bility of someone changing measurement profiles thatmay result in improper ALarm activation or inaccuratemeasurements.
RMS Detection and LOG Conversion. The output ofthe analog switch goes to the RMS detection and Loga-rithmic conversion section of the SLARM™. The RMSdetector is a true RMS detector able to handle crestfactors of 5–10. This is different from an averagingdetector set up provide rms values from sine wave (lowcrest factor) inputs. The response of the detectorexceeds the response limits of the SLARM™.
The output of the RMS detector is fed to the Log(Logarithmic) converter. A logarithmic conversion rangeof over 100 dB is obtained. The logarithmic output thengoes to the A/D section of the microcontroller.
Microcontroller. The microcontroller is the digitalheart of the SLARM™. A microcontroller (MCU) doesall the internal calculations and system maintenance.
SPL, Leq. The digital data from the internal A/D isconverted by the MCU to supply dBSPL, and Leqvalues for both storage in the on-board flash memoryand inclusion in the data stream supplied to the USBand serial ports. These are complex mathematical calcu-lations involving log and anti-log conversation andaveraging.
The SPL values are converted to a rolling average.The results are sent to the on-board flash memory thatmaintains a rolling period of about 2 to 3 weeks.
Leq generation in the SLARM™ involves two inde-pendent calculations with two programmable periods. Aset of complex calculations generates the two Leqvalues.
Thresholds and Alarms. The results of the Averagingand Leq calculations are compared by the micro-
controller with the Threshold levels stored in theon-board ferro-ram. Threshold levels and types—SPLor Leq—are set using the Settings tools provided inSLARMWatch™. These thresholds are updated by theSLARMScheduler™ routine.
If the programmed threshold limits are exceeded themicrocontroller generates an output to an external driverIC. The IC decodes the value supplied by the microcon-troller, lighting the correct front panel ALARM LED,and also activating an opto-isolator switch. Theopto-switch contacts are phototransistors. The tran-sistor turns on when the opto-isolator LED is activated.The result—a contact closure signaling the outsideworld of the ALarm.
Real-time Clock. The SLARM™ has an on-boardreal-time clock. Operating from an internal lithium cell,the real-time clock timestamps all of the recordedhistory, event logging, and controls the SLARMSched-uler™ operation. The Settings panel in SLARM-Watch™ allows user synchronization with a PC.
Communicating with the Outside World. SLARM™may be operated Standalone (without a PC). TheSLARM™ provides both USB 2.0 and RS232 serialconnections. The USB port is controlled by the micro-controller and provides full access to the SLARMsettings, History flash memory, and firmware updatecapability.
The RS232 is a fully compliant serial port capable ofup to 230 k Baud. The serial port may be used tomonitor the data stream from the SLARM™. The serialport may also be used to control the SLARM™ settings.
Ethernet and Beyond. Utilizing the wide variety ofafter-market accessories available, the USB and Serialports of the SLARM™ may be connected to theEthernet and Internet. RF links like Bluetooth® andWiFi are also possible. Some accessories will permit theSLARM™ to become an Internet accessory without aPC, permitting remote access from around the world.
The SLARMSoft™ package permits the monitoringof multiple SLARM™s through the SLARMNet™. TheSLARMAlarm™ software not only provides a simpledigital display of multiple SLARM™s also permitstransmission of SMS, text and email of ALarm events.This transmission provides the SLARM™ ID, Time,Type, and Level information in a short message. Theworld is wired.
History. The on-board flash and ferro-ram memoriessave measurements, events, settings, user access, andthe SLARM™ Label. The SLARM™ updates the flashmemory every second. SPL/Leq data storage is on a
rolling 2 to 3 week basis. ALARM events, user access,and setting changes are also logged. These maybedownloaded, displayed, and analyzed using featuresfound in SLARMWatch™.
47.5.1.3.1 Applications
SLARM™ applications are virtually unlimited.Day–to–day applications are many. Children’s day carecenters, hospitals, classrooms, offices, clubs, rehearsalhalls, auditoriums, amphitheaters, concert halls,churches, health clubs, and broadcast facilities areamong the locations benefitting from sound level moni-toring. Industrial and community environments include:machine shops, assembly lines, warehouses, marshal-ing yards, construction sites and local law enforcementof community noise ordinances.
The following are examples of recent SLARMSolu-tion™.
A Healthy Solution. Located in an older building witha lot of flanking problems, the neighbors of a smallwomen’s health club were complaining about the musicused with the exercise routines. Negotiations were at astandstill until measurements were made.
Music levels were measured in the health club and amutually acceptable level established. A SLARM™(operating standalone—no PC) was installed to monitorthe sound system and a custom control accessory devel-oped to the customer’s specifications. If the desired SPLlimits were exceeded for a specific period of time, theSLARM™ disabled the sound system, requiring amanual reset. The result, a Healthy Solution.
Making a Dam Site Safer. A SLARM™ (operatingstandalone—no PC) combined with an Outdoor Micro-phone assembly (ODM) located 300 ft away, monitorsthe 140+ dBSPL of a Gate Warning Horn. The operatorover 100 miles away controls the flood gates of the dam,triggering the horn. The PLC controls the gate operationand monitors power to the horn but not the acousticoutput. The SLARMSolution™ monitors the sound levelfrom the horn. The thresholds were set for the normallevel and a minimum acceptable level. The minimumlevel alarm or no alarm signal prompts maintenanceaction. The SLARM™’s history provides proof of properoperation. Alarm events are time-stamped and logged.
Is It Loud Enough? Tornado, fire, nuclear power plantalarms and sirens as well as many other public safetyand industrial warning devices can benefit from moni-toring. Using the SLARM™’s standalone operation and
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the ODM microphone assembly make these remoteinstallations feasible.
A Stinky Problem. A Me di v ac h e l i c o p t e r on i t slife-saving mission quickly approaches the hospitalhelipad and sets down. On the ground, the helicopterengines idle, prepared for a quick response to the nextemergency.
The problem: the exhaust fumes from the enginesdrift upward toward the HVAC vents eight storiesabove. Specialized carbon filters and engineering staffrun to the HVAC controls to turn them off—oftenforgetting to turn them back on, costing the hospitalover $50,000 a year and hundreds of manhoursprovided limited success.
A standalone SLARM™ with an ODM microphonemounted on the edge of the helipad detects arrivinghelicopters and turns off the HVAC intakes. As the heli-copter departs, the vents are turned back on automati-cally. The SLARM™ not only provides control of theHVAC but also logs the arrival and departure events forfuture review, Fig. 47-9.
Too Much of a Good Thing Is a Problem. Noise com-plaints are often the result of Too Much of a GoodThing. A nightclub housed on the ground floor of acondo complex faced increased complaints from bothcondo owners and patrons alike.
The installation of a SLARM™ connected to theDJ’s and sound staff’s PC allowed them to monitoractual sound levels and alarm them of exceedance. Thecombination of the SLARM™’s positive indication ofcompliance and accidence assures maintenance ofproper levels.
Protecting the Audience. Community and nationalregulations often specify noise limits for patrons andemployees alike. Faced with the need to assure theiraudiences’ hearing was not damaged by Too Much of aGood Thing, a major broadcast company chose theSLARMSolution™.
Two SLARM™s were used to monitor stage andauditorium levels. These units made use of both SPLand Leq Alarm settings. In addition, SLARMAnal-ysis™ is utilized to extrapolate daily Leq and dose esti-mates. The installations used the standard SLARM™mic package and ACO Pacific’s 7052PH phantommicrophone system. The phantom system utilized themiles of microphone cables running through thecomplex. This made microphone placement easier. Theresults were proof of compliance, and the assurance thataudience ears were not damaged.
NAMM 2008 – Actual Measurements from the Show Floor. A SLARM™ was installed in a booth at theWinter NAMM 2008 show in Anaheim, CA, Themicrophone was placed at the back of the booth about8 ft above the ground away from the booth traffic(people talking).
The following charts utilized SLARMWatch™’sHistory display capability as well as the SLARMAnal-ysis™ package. The SLARM™ operated standalone inthe booth with the front panel LEDs advising the boothstaff of critical noise levels.
The charts show the results of all four days ofNAMM and Day 2. Day 2 was extracted from the datausing the Zoom feature in SLARMWatch™. The boothwas powered down in the evening, thus the Quietperiods shown and the break in the history sequence.The floor traffic quickly picked up at the beginning ofthe show day.
An 8 hour exposure at these levels has the potentialof permanent hearing damage. The booth was located inone of the quieter areas of the NAMM Exhibition floor.Levels on the main show floor were at least 10–15 dBhigher than those shown on the graphs.
47.6 Summary
We live in a world of sounds and noise. Some is enjoy-able, some annoying, and all potentially harmful tohealth. Devices like the SLARM™ represent a uniqueapproach to sound control and monitoring and a usefultool for sound and noise pollution control. We hope wehave provided insight into how much sound—noise tosome—is part of our world to enjoy responsibly, Alsoso alerting you to the potential harm sound represents.
Figure 47-10. This is a dBA (A weighted SPL) for all 4 daysof NAMM- The booth power was shut down in the eveningand then turned on for the exhibition. The SLARM™restarted itself each morning and logged automaticallyduring this time. It was not connected to a computer. Theblack indications are of sound levels exceeding the thresh-olds set in the SLARM™. Courtesy ACO Pacific.
Figure 47-11. All four days 15 s LeqA. Courtesy ACOPacific.
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Leq(dt) – 80.58 dB : Duration – 1:00:00SLARMAnalysis™ Calclation of a 1 hour Leq
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Figure 47-12. Day 2—a typical day. This chart is the Leq(15 s) dBA. This basically represents the running averagesound level. Courtesy ACO Pacific.
