priate hearing protection devices. On thesurface, this may look like one of the morestraightforward elements in a com-prehensive hearing conservation program.It is not. In fact, because of improperselection, fewer workers are wearing theirhearing protection — and thus exposingthemselves to potential hearing loss —than might otherwise be the case.

In British Columbia, we define anHPD as a device that will "…reduce,or attenuate, the level of noisereaching the ear by blocking the earcanal or by covering the "ear"(Workers' Compensation Board ofBritish Columbia, 1989). There aretwo main types of HPDs —earmuffs and earplugs.

The tricky part for most of us isdefining and applying the concept ofappropriate HPDs. How exactly isthis determined? HPDs are ratedaccording to Standard Z94.2,Hearing Protectors, of the Can-

adian Standards Association (CSA). Thestandard assigns each HPD to one of threeclasses of protection based solely on atten-uation values: Class A, Class B and ClassC. Class A protectors have the greatestattenuation, Class B less than A, and ClassC less than B. Attenuation figures areobtained at independent test laboratories(usually in the United States) by the man-ufacturers of the products and are easilyavailable; they are typically printed onsales brochures. The CSA hearing standardcontains a "Table AI," which gives therecommended class of HPD for certainnoise exposures (see Table I on page 51).

I hesitate to include this table because

HEARING PROTECTION

Hearing protection attenuationIs more really better?

When choosing hearing protection, people tend to look at Table lA in Canada's hearingprotection standard and declare that Class A protectors must be the best because they offer

the highest attenuation — end of discussion. But this approach is full of problems,not the least of which is its potential to discourage the use of hearing protection.

By Christine Harrison

oise is the mostprevalent hazardousenvironmental factor

in industry (Phaneuf and Hetu,1990). It is not surprising, there-fore, that noise-induced hearingloss is the most common perma-nent occupational disease in industrializedcountries (Hem and Getty ,1991). In recognition of the needto put an end to this highly preventabledisease, many industrial countries haveinstituted hearing conservation programs,which usually contain the following ele-ments:(1) identifying hazardous areas through anoise survey;(2) eliminating or reducing noise atthe source;(3) posting warning signs;(4) providing appropriate hearing protectiondevices (HPDs);(5) providing periodic hearing tests;(6) educating workers as to the effects ofnoise exposure and the need for consistentuse of HPDs for all on- and off-the-jobnoise exposures; and(7) — one that many in the hearing con-servation field would add — compensatingand rehabilitating workers suffering fromoccupational noise-induced hearing loss.

It is the fourth of these components that Iwill focus on — providing appro-

Page 1

An active nonlinear (or electric)hearing protection device has a

microphone on the outside of theearmuff, which transmits sound to

the inside via a small speaker.

Christine Harrison, B.A., M.Sc., Aud. (C), is an occupational audiologist with the Workers' CompensationBoard of British Columbia in Richmond, B.C.

too much emphasis is placed on it as the single determining factor in the selection of HPDs. Notethat the noise exposure portion of the table refers to the eight-hour equivalent noise exposure ofindividual workers, not the noise level of pieces of machinery or equipment.

For example, an industrial chainsaw can produce sound levels in excess of 110 dBA, but due towork stoppages throughout the day, the eight-hour equivalent (also called Leq8 or Lex) is closer to102 dBA. When reading the table, it is the "102" that applies, not the "110+."

This is a very common misconception about how to use the table and has led to theinappropriate notion of "classes of noise." I have heard workers and employers refer to areas of aworksite as "Class A areas." They mean the noise level of equipment in those areas exceeds 95dBA and, by misinterpreting the table, assume that workers must wear Class A hearing protection.The inappropriate application of this table is a constant source of aggravation for the occupationalaudiologists at the B.C. WCB in our interactions with industry.

There are several other items I would like to point out about the hearing protection standard:(I) The class of HPD is recommended, not required.(2) The table of recommended classes is not a mandatory part of the standard; that is, a user maydisregard the table.(3) The standard mentions that other factors besides noise exposure should be taken into accountwhen selecting an HPD. These include hearing loss (if any), use of other protective equipment,anatomical peculiarities (head size or shape, ear canal size or shape), and comfort.(4) Hearing protectors must be provided on an individualized or personalized basis.

These provisions in the standard are rarely appreciated and even more rarely applied inindustry. Most people get only as far as the table and assume that since Class A HPDs have themost attenuation, they must provide the most protection. They then decree that Class A is the"best," issue it to everyone, and stringently enforce the wearing of it — end of discussion.

50 OH&S CANADA/ 1993 BUYER’S GUIDE

Page 2

Figure 1

Hearing protection use(All industry in British Columbia)

BMuff7%

A Plug28%

A Muff30%

B Plug1% NoH.P

35%

A Plug42%

BMuff3%

A Muff23%

B Plug3%

NOH.P.29%

Yes ! A comparison of HPD use in indus-try in B.C. between 1981 and 1991 helpsexplain why (see Figure I above). Thisinformation was collected during the annu-al hearing test that employers of theprovince provide to all noise-exposedworkers. The records have been stored oncomputer since 1978. Recorded HPD useamong workers is reflected by the numberof workers who were tested. In 1981, 74,720were tested and in 1991, 142,022 weretested.

While it is encouraging to see the non-use of hearing protection ("No HP") dropfrom 35 per cent to 29 per cent, 29 per centnon-use is still unacceptable. Note, too, therelatively low use of Class B protection in

they resist using HPDs, but I have 16 yearsof experience in occupational audiology andcollect much anecdotal information. Mysources include workers, employers, healthand safety personnel, audiometrictechnicians, salespersons, physicians, andmore. The most common complaints I hearabout HPDs, from users and non-users alike,are the following:.I cannot hear warning signals or speech. .Icannot perform the job confidently orefficiently..The heat and weight of the protectiondevice is excessive (largely among ear-muffwearers)..The HPD is incompatible with wearingother protective devices.

Yes, we have a problem — 29 per cent ofworkers involved in hearing conservationprograms in B.C. do not use hearingprotection. Furthermore, not all of the other71 per cent are happy with the HPDs thattheir employers provide.

These workers receive annual hearingtests. In B.C., this also means annualcounselling about the extent of their hear-ing loss (if any) and annual counsellingabout the importance of wearing hearingprotection. In addition, employers mustprovide HPDs at their expense (WorkersCompensation Board of British Columbia,1980). What this suggests is that workerinability to pay for HPDs or the lack ofknowledge about the need for HPDs cannotexplain the resistance to wearing them.

both 1981 and 1991: eight per cent and sixper cent respectively.

We estimate that 90 per cent of B.C.workers are exposed to daily equivalentnoise levels (Leq8 or Lex) of less than 95dBA. According to the CSA standard, ClassB protection is recommended for this levelof exposure. The use of Class C protectionis so limited that we do not collect thisinformation.

Table 1

• Leq less than 85 dBA

• Leq up to 89 dBA

• Leq up to 95 dBA

• Leq up to 105 dBA

• Leq up to 110 dBA

• Leq more than 110 dBA

Page 3

• No protection required

• Class C

• Class B

• Class A

• Class A plug + Class A or

Class B muff• Class A plug + Class A or

Class B muff and limitedexposure

• We have not yet been able to conduct for-mal research with our workers about why

The issue is not what is wrong with theseworkers, but rather what is wrong with theapproach to the provision of HPDs? I sub-rnit that it is the "Class A is best" approachthat is the problem. Examination of anyattenuation figures will reveal that tradi-tional HPDs are more effective at reducinghigh frequency sounds than low frequencysounds. If we know that both human speechas well as many machine sounds containboth high and low frequency sounds, then itfollows that conventional HPDs will alter,or distort, the signal. Couple this distortingeffect with the excessively high attenuationof Class A protectors, and you have a recipefor worker rejection and non-use. And theworkers are reporting this loud and clear.

51 OH&S CANADA/ 1993 BUYER’S GUIDE

SSeelleeccttiioonn ooff HHeeaarriinngg PPrrootteeccttoorrssMaximum equivalent Recommended classNoise level, dBA of hearing protection

Page 4

53 OH&S CANADA/ 1993 BUYER’S GUIDE

The contention here is that conven-tional Class A HPDs are not necessarily thebest choice for workers. This is a concernfor all workers, but even more so forworkers with hearing impairments (Abel,1992). Even without hearing protection,their hearing loss may cause speech andmachine sounds to sound distorted. Thisproblem may be compounded by the use ofan HPD (Abel, et al., 1982, Berger, 1992).

First, abandon the conventional approach tothe provision of HPDs. I do not advocateabandoning the so-called conventional HPD,just the rigid, non-personalized approachthat is all too common. Consider eachworker as an individual who requirespersonalized fitting of his or her HPD.Second, consider other types of HPDs.Many manufacturers acknowledge thelimitations of conventional HPDs and aredesigning products that attempt to addresscommunication difficulties specifically.

Lower overall attenuation: There are HPDsthat provide moderate as opposed tomaximum attenuation. This is not a newconcept, just a recognition of the existenceand potential usefulness of Class B (or evenClass C) protectors. Examples of Class Bprotectors include earmuffs, earplugs and atype of earplug sometimes known as a canal-cap.Built-in communications systems: Manymanufacturers produce, or will modify,HPDs that incorporate protection along withcommunications capabilities. These devicescan be hands-free, hard-wire, or PM wirelesssystems. Many types are available, usingboth earmuffs or earpugs.Flat attenuation: Hearing protectors areavailable that provide equal attenuation at allfrequencies — allowing the spectral, orfrequency, relationship of the signal to bepreserved and not distorted. Originallydesigned for musicians, I foresee great

52 OH&S CANADA/ 1993 BUYER’S GUIDE

potential for the application of these pro-tectors in industry. Both custom-molded andpre-molded versions are available, withattenuations ranging from 15 to 25 dB.Nonlinear attenuation: There are two typesof these HPDs -passive and active nonlinear(Berger, 1992). The passive HPD usuallyhas a sharp-edged opening that permitssound to come through. At low levels ofoutside noise, this protector offers a certainamount of attenuation; above a certainexternal noise level, usually 120 dB, theattenuation of the HPD increases. Passivenon- linear HPDs are available as earmuffsor as custom-molded earplugs.

The active nonlinear HPD is also knownas an electronic HPD. A microphone picksup sound outside the earmuff and transmitsit to the inside of the earmuff via a smallspeaker. A volume control permits actualamplification of out- side sounds and can beadjusted for more or less amplification.When the sound inside the earmuff gets toabout 85dB, the electronics start to act as alimiting device

and do not permit further amplification.It is important to point out that two

versions of this HPD are sold: monaural(one external microphone) and stereo (twoexternal microphones). The stereo versionshould be used by workers who need tolocate the source of sounds (Noble, et al.,1990).

I stress that there is no single solution tothe problems experienced by users andnon-users of HPDs. Many workers arequite happy, productive and safe usingconventional hearing protection. How-ever, it is clear that a conventionalapproach is not suitable for everyone - inmy opinion, for no one. I make a cleardistinction between conventional HPDsand a conventional approach to theprovision of HPDs -they are not the same.

None of the protectors I have dis-cussed is a cure-all. All workers must

be viewed as individuals with individualneeds, and I bring these newer technolo- gyprotectors to your attention as options to beconsidered. The current CSA standard hasvery valuable advice in its Appendix A. Iadvise you to read it and take it to heart.

A very prominent figure in audiolo- gy,Dr. Aram Glorig, once said the bestprotector is the one which is worn. Giventhat there are many differences amongworkers, it seems reasonable to deduce thata variety of HPDs are need- ed to satisfyindividual needs. We must expand, notreduce, the selection avail- able to eachworker.

I firmly believe that more is better - notmore attenuation, but more choice.

.Abel, S.M., 1992, Signal Detection and SpeechPerception in Noise with Level-Dependent HearingProtectors. Mount Sinai Hospital: Toronto..Abel, S.M., Alberti, P.W., Haythomthwaite, C., andRiko, K., 1992, "Speech intelligibility in noise: effectsof fluency and hearing protector type," in Journal ofthe Acoustical Society of America, 71(3),708-715.

.Berger, E., 1992, "F1at-response, moderate-atten- uation, and level-dependent HPDs: howthey work, and what they can do for you," inPapers on Hearing Protection presented at theCOPE '92 Conference on Protective Equipment.Canadian SafetY Council, Ottawa..Canadian Standards Association, 1984, Z94.2-M1984, Hearing Protectors, CanadianStandards Association: Toronto..Hetu, R. and GettY, L., 1991, "The nature ofthe handicaps associated with occupationalhearing loss: implications for prevention," inOccupational Noise-lnduced Hearing Loss:Prevention and Rehabilitation. NationalOccupational Health and Safety Commission:Sydney; University of New England: Arrnidale..Noble, W.G., Murray N., and Waugh R., 1990,"The effect of various hearing protectors onsound localization in the horizontal and verticalplanes," in American Industrial HygieneJournal, 51(7), 370-377..Phaneuf. R. and Hetu, R., 1990, "An epidemio-logical perspective of the causes of hearing lossamong industrial workers," in Journal ofOtolaryngology, 19, 31-40..Workers' Compensation Board of BritishColumbia, 1980, Industrial Health & SafetyRegulations. Workers' Compensation Board ofBritish Columbia: Vancouver..Workers' Compensation Board of BritishColumbia, 1989, Hearing Protection in NoiseIndustry. Workers' Compensation Board ofBritish Columbia: Richmond .HI