Puaonal Radio Headsets
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`CONTRIBUTING EDITORS
`
`Clifford R. Bragdon
`
`Aram Glorig
`
`Gregg K. Hobbs
`Donald R. Houser
`
`George F. Lang
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`Paul B. Ostergaard
`
`- Mark C. Rodamaker
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`Anthony J. Schneider
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`Alice H. Suter
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`Richard H. Tuft
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`John E. Wesler
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` EDITOR AND PUBLISHER
`
`dack K. Mowry
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` Randall J. Allemang
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` Chris D. Powell
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`Larry H. Royster
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` Eric E. Ungar
` Donald Wasserman
`
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` Lyle F. Yerges
`
` CIRCULATION MANAGER
`
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` Anne Morgan
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` NEWSEDITOR
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`Helen Hess
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`ART DIRECTOR
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`Gerald F. Garfield
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`VBPA MEMBER
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`SS PUBLICATIONS
`BU:
`AUDIT OF CIRCULATION
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`AMERICAN BUSINESS PRESS
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`ABP
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`Sound and Vibration « May 1985
`
`
`
`
`
`
`
`THE NOISE AND VIBRATION CONTROL MAGAZINE
`Noise and Vibration Control © Structural Analysis
`Dynamic Measurements ¢ Dynamic Testing
`Hearing Conservation @ Architectural Acoustics
`
`MAY 1985
`
`VOLUME 19/NUMBER 5
`
`Editorial
`Should the Walkman Take a Walk?
`Larry H. Royster
`
`Features
`- DoPersonal Radio Headsets
`Provide Hearing Protection?
`S. F. Skrainar, L. H. Royster, E. H. Berger and R. G. Pearson
`Altermatives for
`Hearing Loss Risk Assessment
`John Erdreich
`Audiometric Evaluations for
`industrial Hearing Conservation
`Julia Doswell Royster
`
`
`Departments
`S)V News - 1
`S)V Observer - 6
`Our Authors - 6
`
`Products and Literature — 30
`Professional Services - 32
`Advertiser's Index -— 34
`
`5
`
`16
`
`22
`
`24
`
`Cover
`One method ofassessingthe attenuation of circumaural hearing protection
`devices is the dummy head specified in the supplemental physical method of
`ANSI S3.19-1974. An 8-kg version of that head, machined from cast alu-
`minum and covered with an experimentalartificial flesh, is shown here during
`the testing of the insertion loss ofa setoflightweight plastic earmuffs. (Photo
`courtesy of E-A-R Division, Cabot Corporation, Indianapolis, IN.)
`
`
`Copyright © 1985, Acoustical Publications, Inc., 27101 E. Oviatt Ad., P.O. Box 40416, Bay Village, OH 44140.
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`internatreference use, may be obtained from the publisher. ISSN 0038-1810/81 $2.00. Copies of SOUND AND
`VIBRATION In microtiim are available trom: University Microfilms, 300 N. Zeeb Rd., Ann Arbor, Ml 48106. Prices
`on request.8
`ons:SOUND AND VIBRATION Is published 12 timesa year.itis circulatedwithout charge
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`~~ | this material may beprotected by Copyright law (Title 17 U.S. Code)
`
`Do Personal Radio Headsets
`Provide Hearing Protection?
`
`Stephen F. Skrainar, North Carolina State University, Raleigh, North Carolina
`Larry H. Royster, North Carolina State University, Raleigh, North Carolina
`E. H. Berger, E-A-R Division, Cabot Corporation, Indianapolis, Indiana
`Richard G. Pearson, North Carolina State University, Raleigh, North Carolina
`A laboratory investigation was conducted to determine the
`acoustic attenuation of 18 personal radio headsets. Sixteen
`supra-aural, two semi-aural, and two circumaural headsets
`included. Insertion
`
`orated
`threshold values derived via the methodology ofANSI S3.19-
`1974, The results demonstrated a range of NRR-like numbers
`from 0.3 to 2.6 dB. Across devices and angles ofincidence, the
`circumaural devices provided up to 7 dB amplification at 800
`Hz and all ofthe devices significantly affected the sound spec-
`trum at
`above 2 kHz. The results ofthis
`tion indicate that, in general, personal radio headsets do not
`significantly modify external soundfields as perceived at the
`eardrum.
`
`Today it is almost impossible to miss seeing someonewalk-
`ing, running, cycling, driving, and in some instances, working
`while listeningto a personal radio.Since their introduction to
`the commercial marketin 1979 by the Sony Corporation,these
`devices, commonly referred to as “Walkmans,” have become
`exceedingly popular.
`In the past two to three years several articles have been writ-
`ten on personal radios andtheir potential dangers.'* The gen-
`eral tone of these articles is that these units may present
`hazards in the following areas:1.they distract the user's atten-
`tion; 2.they interfere with the perception ofincoming auditory
`information such as communication and warning signals; and
`3. they may cause noise-induced hearing loss.
`In 1982 the town ofWoodbridge, New Jersey passed legisla-
`tion prohibiting the use of personal radios on the streets of
`their town. The township council President was quoted as say-
`ing “I think it’s a distraction.”* The danger,they feel, is that
`users of personal radios will be oblivious to traffic hazards.’
`The United States Postal Service,in a similar action, banned
`the use of personal radios, with few exceptions, by postal
`employees while on the job.'° They contended that an
`individual's “concentration to traffic conditions can be com-
`promised by headphones,” and that “they (headsets) can also
`be ahazard when performingjobs where an auditory alarm or
`feedback is essential ...”
`Werecently investigated”’ the potential for personal radios
`to contribute to noise-induced hearing damage. The study
`concluded that,at least for the one industrial noise environ-
`mentinvestigated,the use of personal radiosby employeesdid
`nol present a significant additional health hazard and that
`their use should be allowed. However, the study did recom-
`mendcertain criteria be followed to educate the employee
`population to the potential dangers of extended use of per-
`sonal radios played at high volume levels, and to insure that
`potentially noise-sensitive employees are identified and
`refused permission to continue the use of personal radios
`while on the job.
`Whendiscussing the potential danger of personal radios
`interfering with incoming auditory information, one consider-
`' ation is the attenuation characteristics of personalradio head-
`sets. Huber strongly advocates that “none of the units on the
`market can reduce sound, nor could any of these headsets be
`rated able to attenuate sound as supplemental hearing protec-
`tion.”* Unfortunately, Huber did not supply objective data to
`substantiate his claim.
`
`
`
`
`rgure 1. Orientation coordinates for sound sources relative to the
`[AR manikin.
`
`
`
`Figure 2. Supra-aural, semi-aural, and circumaural headsets,
`
`The purpose ofthis study, therefore, was to provide objec-
`tive data concerning the insertion loss characteristics of per-
`sonal radio headsets to facilitate management decision-mak-
`ing policy regarding personalradio use in industrial settings.
`Meth
`The insertion loss, defined as the difference between the
`eardrum sound pressure levels (SPLs) with and without the
`headphones in place, was measured using KEMAR."? '3
`KEMAR was specifically designed to simulate the acoustic
`characteristics of the human ear, head, and uppertorso, in-
`cluding a Zwislocki coupler to model eardrum impedance.
`KEMAR includes geometrically accurate pinnas but was not
`designed to reproduce the dynamic properties ofaural and cir-
`cumaural flesh, nor the bone conduction pathwaysto the inner
`ear. Therefore,it was deemed important tojustify the insertion
`loss data obtained using KEMAR with theresults of real-ear
`attenuation at threshold valuesderived via the methodologyof
`ANSI S3.19-1974."*
`Measurements Using KEMAR. Measurements were taken in
`a semi-free field. KEMAR was exposedto while noise generat-
`ed by a Calrad minicuvve air-suspension speakerpowered bya
`Realistic SA100B amplifier driven by a GenRad 1382 random
`noise generator. Measurements were taken at 0° and 90° inci-
`dence angles. These incidence angles follow Burkhard’s con-
`vention’ (reference Figure 1).
`Eighteen headsets which commonly accompany personal
`
`16
`Sound andVibration « May 1985
`
`3
`
`

`

` *
`
`dieiwssis hab bias g Sve ae eee
`Oke ioe aeee -L5
`DN ae Creek ee ae -2.1
`PG ae acre eee 1.2
`p
`
`
`-15
`
`%
`
`
`
`RR
`radio units were evaluated to determine their insertion loss
`Table 1. A comparisonofthe insertion loss characteristics ofa Pickering
`characteristics. The labelling of headset style generally fol-
`OA-101P (supra-aural)
`measured in a diffuse sound
`field in ac-
`cordancewithANSI$3.19 and in adirectionalSendfeoea
`lows thedefinitions set forth in ANSI $3,19-1974."* In total,
`using KEMAR.
`ine test reco)
`} were completed, sixteen using supra-
`aural headsets(having aheadband and foam pads fitting light-
`insertion Loss (dB)
`One-Third Octave
`ANSI
`Band Center
`ly against the pinna), two using semi-aural headsets (ear-
`Mean Std.Dev. Mean
`Frequency (Hz)
`phones supported inthe conchaofthe ear canal), and twotests
`using circumaural headsets (the earphone enclosesthe entire
`REG ie wists ptieessee she os alee aca oie 13
`2.4
`-0.2
`MOO eee ar eniceeed cea tka ea oe
`-
`-
`-0.4
`pinna) (referenceFigure 2). Two of the headset units had
`DOD aes aie Cee eee reise -
`cies
`-0.3
`removableheadbands allowingthe earphonesto be used in the
`POM or ees ai gie gale ea tigcls eee ae
`0.7
`2.1
`-0.3
`concha(semi-aural), oras typical openair headsets (supra-
`BIG cave etsnaaeeeatces
`~-
`-
`-0.3
`Riera he we eee eda haa gine oa =
`-
`-03
`aural). For the purpose ofthis research the two dual-use head-
`OD i's a inp ase ceie nob loa eiacecelaisead ke =-0.1
`27
`-0.4
`sets were tested as both supra-aural and semi-aural devices.
`-
`-0.7
`A-weighted, C-weighted,and one-third octave band SPLs at
`-
`-1,0
`the center band
`cies from125 Hz to 8 kHz were mea-
`2.0
`=-15
`-
`-2.4
`sured with and without the headphonesin place. An initial
`29
`-3.4
`recording of the “no headphones” condition was conducted,
`3.0
`3.5
`followed by three repetitions of the “headphones on” proce-
`2.7
`0.8
`dure. A final recording of the “no headphones” condition
`3.0
`1.2
`3.1
`6.2
`concluded the measurements.All headsets were evaluated at
`3.4
`13.6
`each of the two incidence angles previously mentioned.
`3.4
`9.0
`The average SPL values for the two test conditions (“no
`3.8
`headphones” and “headphones on”) at the two incidence
`
`
`RaeresecreteNtesdeathsgeeseSpangeneeeeRO
`angles forall the one-third octave band SPL recordings were
`Table 2. A comparison ofthe insertion loss characteristics ces
`- determined. The average value for the “headphoneson” con-
`headse
`OA-88 (supra-aural)
`t measured in a diffuse sound
`field in
`-
`dition was then subtracted from the average valuefor the “no
`headphones” condition at each test frequency. The resulting
`values established the insertion loss characteristics of the
`headphones(in dB)at one-third octave bandcenter frequen-
`cies,
`:
`Comparison to Real-Ear Attenuation at Threshold Data.
`Although KEMAR has beenutilized to measure the insertion
`loss ofhearing protection devices,it was not intendedfor that
`purpose andresults with certain types of devices have shown
`Significant disagreementwith real-ear data.'* '* We did not
`expect such problems with devices of the type includedin this
`study due to their presumed low inherent attenuation and
`their method ofinterface to the ear. However, we decided to
`confirm the acceptability of using KEMAR for our purpose by
`measuring a circumaural and two supra-aural devices by the
`standardized real-ear threshold method of ANSI $3.19 and
`comparing the data to KEMAR measuredinsertionloss values.
`The KEMAR datafor a 0° angle of incidence are compared to
`the ANSI S3.19 valuesin Tables 1-3 and Figures 3-5. Theslight
`differences observed in the measuredinsertion loss values by
`the two methods are probably primarily attributable to the
`directional sound field used for the KEMAR measurements
`versus the diffuse sound field required by the ANSI $3.19
`Table 3. A comparison of the insertion loss characteristicsofa Tandy 12-
`oh accord-
`' methodology. These data confirm the suitability ofKEMAR for
`185 (circurnaural)
`measured in a diffuse sound
`ance with ANSIS3.19 and in adirectionalsoundfield(0°
`J using
`measuring the insertion loss for the style of personal radio
`KEMAR.
`headsets investigated. The S3.19 testing was conductedat the
`E-A-R Div., Cabot Corp. acoustical labs. and the KEMAR stu-
`dies were conducted at North Carolina State University.
`
`anceFiANSIS3.19andin adirectionalsoundfield(0°incidence) using
`~1.0
`
`One-Third Octave
`Band Center
`Frequency (Hz)
`
`Insertion Loss (dB)
`ANSI
`Mean
`Std. Dev. Mean
`2.5
`0.0
`Findings of Study
`-
`0.0
`The predominant style of headphones accompanying per-
`=
`-0.7
`sonal radios are the supra-aural variety. The insertion loss
`2.1
`0.0
`i
`-1.0
`characteristics of the sixteen supra-aural headsets are pre-
`=
`=11
`sented in Figures 6 and 7 along with the results from the two
`1.8
`-3.3
`circumaural and two semi-aural headsets for comparison.
`=
`-10.5
`From Figure 6 (the 0° incidence angle)it is apparent that a
`=
`9.2
`2.6
`-3.0
`small negative insertion loss (amplification effect) is evident
`=
`6.2
`in the 1 to 2 kHz region for the supra-aural headsets. This
`=
`22.0
`trend peaks at -2.1 dB at 2kHzbefore beginningto drop offand
`3.6
`27.3
`showapositive insertion loss (attenuationeffect) throughout
`=
`24.8
`2.2
`15.0
`the rangefrom 4 to 6.3 kHz, At the 8 kHzbandcenterfrequency,
`'
`'
`2.5
`18,0
`a shift from a maximumpositive insertionlosslevel ofroughly
`=
`19.5
`8 dB to anegative insertion losslevel ofapproximately -5 dBis
`2.6
`10.5
`observed. However,due to the significantdifferences between
`2.7
`the data obtained using KEMAR andthe ANSI $3.19 test fin-
`dings (displayed in Figures 3-5), the values at the 8 kHztest
`frequency should be questioneduntil further verification can
`
`Sound and Vibration « May 1985
`
`
`7
`
`be established.
`Theinsertion loss characteristics of the circumaural head-
`
`4
`
`

`

`-——* KEMAR, O°AZIMUTH
`——* re ANSI 62.10
`
`o
`
`INSERTIONLos
`
`2K
`125 260 60O 1K
`Frequency in Hertz
`
`4K 8K
`
`125 250 500
`
`1K 2K 4K 8K
`
`FREQUENCYIN HERTZ
`
`-——« KEMAR,O*AZIMUTH
`——s re ANSI 83.19
`
`
`FREQUENCY IN HERTZ
`
`
`the supra-aural headsets (1.25 kHz) providing a greater mag-
`nitude ofattenuation through the frequency range of 1.25 to 5
`kHz than for the supra-aural headsets.
`Figure 6 also shows theinsertion loss characteristics of the
`{wo semi-aural headsetsat the 0° incidence angle. There is a
`very slight trend towards negative insertion loss beginning at
`approximately500Hz, reaching a maximum ofroughly -1.7dB
`at 1.6 kHz. A crossoverto a positive insertion loss occurs at
`roughly 2 kHz, reaching a maximumpositive insertion loss of
`approximately 5 dB at 3.15 kHz.
`Figure 7 shows a graphicillustration of the insertion loss
`characteristics for the supra-aural, circumaural, and semi-
`aural headsets at a 90° angle of incidence from the noise
`source.At the 90° orientation a slight increase in the magni-
`tude in sound transmitted to the eardrumis observed overthe
`frequencies exhibiting amplification. This should be antici-
`pated since the sound wave can more effectively couple to the
`headsets atthis angle.A similar increase in the eardrum to the
`free-field transformation ratio is observed,'!
`The average overalleffect of the personal radio headsets on
`an individual's noise exposure was determined by assuming
`an exposure fo a flat (pink) noise spectrum. The reduction in
`this noise spectrum was calculated by subtracting the headset
`insertion loss values from it to determinethe interior (under-
`the-headset) noise levels. The difference between the exterior
`C-weightedandinterior A-weighted SPLs was then computed.
`These values are similar to Noise Reduction Ratings (NRR).'?
`They do notinclude a spectral uncertainty contribution and
`are lacking a two standard deviation correction.
`
`1K 2K 4K ax
`125 250 500
`FREQUENCY IN HERTZ
`
`2K 4K Ox
`128 260 600 1K
`Frequency in Hertz
`
`Figure z Insertion loss characteristics ofpersonal radio headsets at 90°
`azimuth.
`
`128 260 600 1K 2K
`
`4K 6K
`
`Figure 5. Insertion loss characteristicsfora lo 12-185 circumaural
`headset (Note: change in scale in comparison to Figures 3 and 4),
`‘set variety at a 0° incidence angl. are also presented for com-
`parison in Figure 6. Again,a negative insertion loss is observed
`through the frequency range of 500 Hz to 1 kHz. The magni-
`tude ofthis amplification, reaching -6 dB at roughly 630 Hz, is
`greater than that of the supra-aural variety. A positive inser-
`tion loss is evident begining at a lower frequency than thalof
`
`Sound and Vibration « May 1985
`
`5
`
`

`

`
`
`2.
`
`3.
`
`4.
`
`5.
`
`12.
`
`13.
`
`14,
`
`15.
`
`16.
`
`Conclusion
`Theresultsof this research indicate thatthe typical personal
`radio headsets studied (those which commonly accompany
`“Walkman”style radios) do notsignificantly alter the sound
`field reaching the eardrum,and they do notprovide any signif-
`icant degree of hearingprotection.
`
`Acknowledgements
`This research was supportedin part by a traineeship award
`in OccupationalSafety to thefirst author undertraining grant
`5-T-15-OH-07101 from the NationalInstitute of Occupational
`Safety and Health, CDC, DHHS.
`
`
`Table 4. Modifed NRRs (see lest), dB.
`Fantel, H. (1983), peraingLights Flash forEarphone Users,”The
`New York Times, July 24,
`Sec. 2, 19.
`Numberof
`Modified NRR, dB
`joes. H. (1982), “Headphone Radios,” Professional Safety,
`Samples
`Headset Style
`0° Incidence 90° Incidence
`uber,L.J. (1984), “Headsets are Hi-Fi Hazards,”NationalSafety
`Supra-Aural 62.0... ..ee eases 16
`0.3
`0.3
`News, Juz, 43-46,
`Semi-Auraliiis's50ss.0ccces ves
`2
`0.6
`2.6
`Katz, A. E., Girstman, H.L., Sanderson, R. G., and Buchanan, R.
`Circumaural ..........ese05 2
`19
`1.2
`(1982), “Stereo Earphones and H
`Loss,” The New England
`JournalofMedicine, Vol. 307, 1460-1461,
`The predicted effect on an individual's noise exposure level
`Kidder,
`M. (1982), “Bann
`the Walkman: What Does It
`as a result of the insertion loss characteristics for the three
`Mean?,” The Christian Science Monitor, Sepl. 8, 22.
`__ headset styles investigated at both the0° and90° incidence
`Lohr, S. (1982), “Headsets and Ear Damage,” TheNew York Times,
`angles is presented in Table 4, The results of this analysis
`July 17, 12>
`Anonymous (1984), “Warning
`of Irreparable D.
`to Hearing,”
`hy
`mentofHealth, Vol. 1,No.2, 1.
`indicate that the protection provided by the personal radio
`Journalofthe Commonwealth
`headsets from the external soundfield is insignificant. In
`5
`(1982), “The Ear-to-Hear Controversy,” Chicago Trib-
`reviewingthe data presented for the semi-aural and circumau-
`une,
`8, Sec. 12, 3.
`ral headsets it must be rememberedthat these results were
`. United States Postal Service (1982), “Personal Portable Radio or
`Tape Cassette faethe PostalBulletin 21379, United States
`based on a small sample size. Nevertheless, no significant
`Postal Service, Was
`on, D.C., Nov. 25, 1-2.
`change in magnitude would be expectedifadditionalunits had
`e Effects on Hearing ofUsing a Personal
`beeninvestigated.
`Radio in an Environment where the DailyimeWeighedAverage
`is 87 dB,” Masters Thesis, Department of Industri
`i
`North Carolina State University, Raleigh, North Carolina.
`Burkhard, M. D. (1978), “Non-hearing Aid Uses of the KEMAR
`Manikin,” in Manikin Measurements, edited
`Burkhard, M.D.,
`Knowles Electronics Inc., Elk Grove Village,
`Illinois.
`Burkhard, M. D, and Sachs, R. M, (1978), ‘Anthropometric Mani-
`kin for Acoustic Research,” in Manikin Measurements, aitedey
`Burkhard, M. D., Knowles Electronics Inc., Elk Grove Village, Illi-
`nois.
`American National Standards Institule (1974), “Measurements of
`Real-earProtection ofHearingProtectors and PhysicalAttenuation
`Earmufis,” Standard $3.19-1974, ANSI, New York, New York.
`Burkhard, M.D. (1978), “Anthropometric Manikin for Acoustical
`Research. Supplementary
`Design Information,” in Manikin Meas-
`urements, edited by Burkhard, M. D., Knowles Electronics Inc., Elk
`Grove V
`, Illinois.
`Berger, E.
`H. (1985) “Methods of Measuring
`‘the Attenuation of
`aeProtection Devices,” submittedfor publication to. Acous.
`‘oc. Am.
`Berger, E. H. (1979), “E-A-R Log 2: Single Number Measuresof
`HearingProtectorNoiseReduction,”SoundandVibration, 13:8,BE
`12-13.
`Learn
`
`References
`1. Bishop,J. E. (1982), “Researchers Say Portable Tape Players with
`Earphones can Cause Hearing Loss,” The Wall Street Journal,
`December2, 14.
`
`17,
`
`Hampton, VA Circle 112 on Reader-Service Card
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