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• Hearing protection

1975

CIS 77-974 Tobias J.V.
Earplug rankings based on the protector-attenuation rating.
A method is proposed aimed at evaluating the effectiveness of ear protectors by a simple numerical rating instead of the rating in dB, which is liable to be misinterpreted. This protector-attenuation rating is based on a 3-digit classification of the mean attenuation and the standard deviation. The test procedure used is the ANSI method for the measurement of ear protectors at threshold. Attenuation spectra of 47 earplugs are reproduced and rated by the proposed classification. The results are tabulated and discussed.
AD-A024 756/9WV, National Technical Information Service, Springfield, Virginia 22151, USA, Oct. 1975. 65p. 17 ref. Price: Photocopy US-$4.50/Microfiche US-$2.25.

CIS 76-1878 Ohlin D.
Army Environmental Hygiene Agency, Aberdeen Proving Ground, Maryland.
Personal hearing protective devices, fitting, care, and use.
This technical guide for hearing conservation discusses: speech communication with protectors, possible noise attenuation, comfort, approved earplugs and earmuffs, proper fitting, an earplug seating device, advantages and disadvantages of earplugs and earmuffs, ear-canal caps, safety helmets with hearing protectors, and techniques for promoting the use of hearing protectors.
AD-A021 408/OWV, National Technical Information Service, Springfield, Virginia 22151, USA, Oct. 1975. 53p. Illus. 11 ref. Price: Photocopy US-$4.50/Microfiche US-$2.25.

CIS 76-1866 Brokmann W.
Personal hearing protection
Persönlicher Schallschutz [en alemán]
This article recalls the permissible noise levels fixed in Germany (Fed.Rep.) as criteria for recommended (85dBA) or mandatory (90dBA) wearing of hearing protection. Personal hearing protection should be chosen on the basis of its noise attenuation factor and physiological comfort in wearing, but the safety aspect should not be sacrificed to these considerations. List of German manufacturers and tables of various types of ear plugs and ear muffs.
Angewandte Arbeitswissenschaft, 1975, No.59, p.42-52. 8 ref.

CIS 76-1579 Von Lüpke A.
Selection of hearing protectors according to their sound attenuation properties
Die Auswahl von Gehörschützern nach ihrer Schalldämmung [en alemán]
The choice of a hearing protector may be based on a precise calculation incorporating the sound spectrum, or derived from an empirical method. In addition to these 2 possibilities, the author describes an approximate method of calculation employing the noise attenuation spectrum of ear protectors. This method yields the reduction in noise level for 3 characteristics of noise frequency.
Kampf dem Lärm, Oct. 1975, Vol.22, No.5, p.128-131. Illus. 3 ref.

CIS 76-970 Dallosta P.M.
A study of proposed ear protection devices for low frequency noise attenuation.
An evaluation of equipment for active and passive noise attenuation has led to the conclusion that passive means were superior. An industrial ear protection market survey and discussions of the ear and noise, earplugs and combinations of attenuation methods are also included in this report.
AD-A009 274/2WP, National Technical Information Service, Springfield, Virginia 22161, USA, Apr. 1975. 143p. Illus. 25 ref. Price: Photocopy US-$5.75/Microfiche US-$2.25.

CIS 76-676 Method for the measurement of real-ear protection of hearing protectors and physical attenuation of earmuffs.
This standard is a revision of the American National Standard Z24.22-1957. It is not appropriate for the evaluation of hearing-protective devices designed to operate exclusively against impulsive noise. Included are: general (scope, real-ear protection method, physical attenuation method, applications); definitions; real-ear method (physical requirements, listeners, test procedures, processing and reporting the data); physical method (test room apparatus, test procedures, reporting the data). An appendix shows the calculation of maximum permissible noise levels.
ANSI S3.19-1974, Acoustical Society of America, 335 East 45th Street, New York, N.Y. 10017, USA. Standard approved on 14 Aug. 1974. 9p. Illus. 4 ref. Price: US-$5.00.

CIS 76-391 Gosztonyi R.E.
The effectiveness of hearing protective devices.
A 5-year study of hearing loss in noise-exposed workers, and of the effectiveness of ear muffs in preventing it. Ambient noise levels in the 3 groups (71 subjects each) were: (1) <60dBA; (2) 76-84dBA; (3) 92-100dBA. Results, shown in graphs and tables, indicate that changes in persons working in areas with noise levels above 90dBA who wear protective devices were no greater than for those working in areas with much lower levels, regardless of the baseline hearing thresholds. A hearing conservation programme including audiometric testing and personal ear protection, utilising a hearing conservation criterion of approx. 90dBA, adequately protects the hearing of noise-exposed workers in areas in which engineering controls are impossible.
Journal of Occupational Medicine, Sep. 1975, Vol.17, no.9, p.569-580. Illus. 6 ref.

CIS 76-383 Industrial noise control and audiometry - Glossary of terms.
A glossary comprising and defining some 500 terms used in industrial noise measurement and control and in audiometry.
National Safety News, Sep. 1975, Vol.112, No.3, p.67-73; Oct. 1975, Vol.112, No.4, p.69-75; and Nov. 1975, Vol.112, No.5, p.79-85. 12 ref.

CIS 76-380 Kroes P., Fleming R., Lempert B.
List of personal hearing protectors and attenuation data.
Noise attenuation data supplied by 40 manufacturers or distributors of hearing protectors (earplugs and earmuffs) are listed in this brochure. The data relate to 175 models; average attenuation values are given (in dB) for the following frequencies: 125, 250, 500, 1,000, 2,000, 3,000, 4,000, 6,000 and 8,000Hz. The 19 laboratories which carried out the relevant tests are also listed. An appendix outlines 3 methods available for the determination of the noise reduction factor of hearing protectors and gives numerical examples regarding their application.
HEW Publication No.(NIOSH)76-120, National Institute for Occupational Safety and Health, 4676 Columbia Parkway, Cincinnati, Ohio 45226, USA, Sep. 1975. 37p. Illus.

CIS 76-496 Trynkowska D.
Influence of measuring conditions on the evaluation of the acoustic attenuation of hearing protectors - Efficacy of combined hearing protectors
Wpływ warunków pomiaru na wartość skuteczności akustycznej ochronników słuchu - Skuteczność akustyczna złożonych ochron słuchu [en polonés]
The investigation was aimed at defining the relation between measurements of the efficacy of hearing protectors and the acoustic conditions in which the measurements were made. Based on the psychoacoustic method of absolute threshold shift in a free sound field and in a diffuse sound field with continuous and intermittent pure tones, the investigation was carried out on 4 different types of hearing protector. In a free sound field with continuous and intermittent pure tones, the same noise attenuation values were obtained in the frequency range of 250 to 4,000Hz, whereas in a diffuse sound field with intermittent pure tones, noise attenuation values lower than those obtained in a free sound field were obtained in the 125 and 250Hz frequencies. The noise attenuation provided by combined hearing protectors (e.g. earplugs/ear muffs) was equivalent, in the 125 to 1,000Hz frequency range, to the sum of the attenuation values (in dB) measured with individual hearing protectors; it was significantly lower (by several dB) than this sum in higher frequency ranges.
Prace Centralnego instytutu ochrony pracy, 1975, Vol.25, No.84, p.41-57. Illus. 14 ref.

CIS 76-97 Tričković K.
Attenuation of perceived noise by the otoneuroprotector - A personal protective device against intense industrial noise
Efekti sniženja percepcije zvuka otoneuroprotektorom - Ličnim zaśtitnim sredstvom kod intenzivne industrijske buke [en serbocroata]
Description of a lightweight muff-type hearing protector and results of tests performed at the Institute for Occupational Medicine (Ni¿, Yugoslavia). The low sound transmission properties of the muffs enable high rates of noise attenuation to be achieved, in the high-frequency bands as well as in the low (by approximately 45-50dB).
IV jugoslovenski kongres medicine rada, Galenika, Masarikova 5/XIX, Beograd, Yugoslavia, 1975, p.685-689. Illus. 3 ref.

CIS 76-91 Howell K., Martin A.M.
An investigation of the effects of hearing protectors on vocal communication in noise.
Although it has been estabished by previous research that the wearing of hearing protectors in noise above 85dB does not reduce speech intelligibility, many workers still complain that verbal communication is impeded by such devices in the working environment. The authors investigated the effects of both earplugs and earmuffs on speech intelligibility for the listener and on the voice level of the talker in the presence of broad-band masking noise. It was found that hearing protectors do not degrade speech intelligibility for the listener and may even effect a slight improvement. However, if worn by the talker, his speech is reduced in level and quality to such an extent that intelligibility for the listener is also reduced. When hearing protectors are worn by both talker and listener, the composite effect is an overall reduction in speech intelligibility.
Journal of Sound and Vibration, 22 July 1975, Vol.41, No.2, p.181-196. Illus. 18 ref.

CIS 76-86 Mimpen A.M., Plomp R.
Noise attenuation effect of 40 different types of earmuffs
De geluidverzwakking van 40 typen oorkappen [en holandés]
The method of measuring the characteristics and noise attenuation in the low and high frequency range of 40 different earmuffs of American, Canadian, Swiss, British, German and Swedish origin are described and the results summarised in a table and discussed. An annex contains individual data sheets for the earmuffs. The influence of the simultaneous wearing of safety spectacles on noise attentuation is studied.
IZF 1975-C10, Instituut voor zintuigfysiologie, Postbus 23, Soesterberg, Netherlands, June 1975. 50p. Illus.

CIS 76-83 Hearing protection
Gehoorbescherming [en holandés]
Following some considerations on structural and technical measures for noise control, this data sheet deals with the noise conditions where the use of ear protectors is recommended or mandatory. To avoid hearing loss, ear protectors must be worn at sound levels above 90dB(A). The various types and the appropriate choice of ear protectors (ear muffs, ear plugs, glassdown), and their noise attenuation properties are surveyed.
P no 138, Labour Inspectorate, Directorate General of Labour (Arbeidsinspectie, Directoraat-Generaal van de Arbeid), Postbus 69, Voorburg, Netherlands, 1975. 12p. Illus.

CIS 75-1995 Brinkmann K.
Testing of hearing protectors at the Federal Laboratory of Applied Physics
Gehörschützerprüfungen in der Physikalisch-Technischen Bundesanstalt [en alemán]
Description of a method for measuring the efficacy of hearing protectors consisting in the double determination of the hearing threshold in 10 persons with normal acuity: test set-up, apparatus used, measurement of hearing threshold, adaptation of protectors, measurement of pressure on the head from the ear-muffs, and test certificate indicating curve of absorption. Tests carried out over a period of several years at the Federal Laboratory of Applied Physics have demonstrated the practical value of this method.
Sicherheitsingenieur, Feb. 1975, Vol.6, No.2, p.68-71. Illus.

1974

CIS 76-974 Michael P.L., Kerlin R.L., Prout J.H., Beaudry B.F.
Environmental Acoustics Laboratory, Pennsylvania State University, University Park, Pennsylvania 16802.
An objective method for evaluating ear protectors.
An artificial test head previously designed and used for the testing of muff-type ear protectors has been modified for the objective measurement of sound attenuation values of insert-type protectors. The apparatus, which consists of a head fitted with an artificial ear and a microphone coupler, is described in detail and the experimental results are given. The attenuation data obtained for some protector models correlate reasonably well with the corresponding subjective findings.
Final report on Grant 5ROI OH 00341-02, National Institute for Occupational Safety and Health, 5600 Fishers Lane, Rockville, Maryland 20582, USA, May 1974. 34p. Illus. 10 ref.

CIS 75-984 Škarinov L.N., Razumov I.K., Denisov Ė.I., Petrjanov I.V., Kozlov V.I., Borisov N.B., Basmanov P.I.
Plugs made from very thin FP-¿ polymer fibres for personal hearing protection
Vkladyši iz ul'tratonkih polimernyh volokon materiala FP-š dlja individual'noj zaščity ot šuma [en ruso]
Description of a new type of disposable earplug, made from very thin polymer fibres (1.5 to 7µm). The plugs are supplied in the form of square pads (4x4cm) weighing 150µg. Before use the square pads are diagonally folded and rolled to tapered plugs. The experimental set-up to test these plugs is described. The sound attenuation measured meets the requirements of the USSR hearing conservation standard GOST 15762-70. A questionnaire survey was carried out among 2000 workers exposed to noise in various industries; 80% of them were in favour of the introduction and regular use of the new earplugs.
Gigiena truda i professional'nye zabolevanija, May 1974, No.5, p.31-35. Illus. 6 ref.

CIS 75-978 Johnson D.L., Nixon C.W.
Simplified methods for estimating hearing protector performance.
Three methods for estimating the noise attenuation effectiveness of hearing protectors are described and evaluated, using typical noise spectra and attenuation data of 33 different protector systems (25 earmuffs, 5 combinations of earplugs and earmuffs, 3 earplugs): NIOSH/OSHA short method; Botsford short method; 2-number method. Noise spectra, hearing protector data and results of the calculations are listed in tables. It is recommended that the Botsford method with a 6dB safety factor be promoted as the best simplified method for evaluating hearing protector performance.
Sound and Vibration, June 1974, Vol.8, No.6, p.20-27. Illus. 6 ref.

CIS 75-676 Waugh R.
Pure-tone, third-octave, and octave-band attenuation of ear protectors.
The difficulties in measuring ear-protector attenuation are stressed; third-octave bands of noise appear to offer a solution to the problem. Experimental work is reported comparing pure-tone and third-octave band measurements of attenuation, calculating octave from third-octave attenuation, and finally comparing the octave-band values so calculated with pure-tone attenuation values. It is concluded that for practical purposes pure-tone and third-octave-band measurements of ear-protector attenuation are identical. The use of pure-tone attenuation values at octave-band centre frequencies as estimates of octave-band attenuation can lead to errors of more than 10dB. In the octaves centred at 500Hz and above, ear-protector attenuation should be measured at third-octave centre frequencies.
Journal of the Acoustical Society of America, Dec. 1974, Vol.56, No.6, p.1866-1869. Illus. 7 ref.

1973

CIS 74-1885 Tisserand M., Krawsky G., Grosdemange J.P., Liévin D.
Personal protection against noise - Method for assessing comfort
Protecteurs individuels contre le bruit - Méthode d'évaluation du confort. [en francés]
For personal protection to be suitable for man, it should not only be efficient but capable of being worn regularly without disturbing the wearer in his work. In the particular case of earmuffs, a review is given of the different stages of comfort evaluation: measurement of the mechanical characteristics of earmuffs; personal testing of earmuffs to obtain a classification according to an overall comfort value; in-depth survey of comfort criteria by questionnaire; development of a method for the calculation of an overall comfort index from mechanical characteristics. A mathematical section is appended.
Cahiers de notes documentaires - Sécurité et hygiène du travail, 4th quarter 1973, No.73, Note No.865-73-73, p.443-452. Illus. 7 ref.

CIS 74-1882 Jungbluth K., Meisel R.
Research on the perception of acoustic signals by workers wearing ear protectors while tamping railway sleepers
Untersuchung über die Wahrnehmung akustischer Signale unter Lärmschutzbedingungen bei Gleisstopfarbeiten und deren Schlussfolgerung [en alemán]
An account of research carried out in conditions close to actual working conditions, to determine whether the wearing of hearing protection while operating mechanical tampers interferes with the perception of acoustic signals. The noise emitted by the tamper was between 97 and 104dBA, necessitating the wearing of hearing protectors. It was found that the perception of acoustic signals was in fact somewhat better when a hearing protector was worn, but that the level of perception was insufficient when intense activity was being carried on. The article concludes that the signalling system used at present is inadequate and recommends the use of electric tampers, revolving or flashing light signals or ear muffs with built-in minireceivers.
Sicherheitsingenieur, Nov. 1973, Vol.4, No.11, p.544-547. Illus.

CIS 74-997 Trynkowska D.
Methods for measuring the sound absorption efficiency of ear plugs
Metoda pomiaru skuteczności tłumienia dźwięków przez ochronniki słuchu typu wkładek [en polonés]
The efficacy of 3 models of ear plugs of Polish, Swedish and East German design was checked by the psychoacoustic method of absolute hearing threshold shift, by the audiometric method and by the objective method of the "real ear". A statistical analysis of the test results shows that the best method for evaluating the sound attenuation afforded by these hearing protectors is the psychoacoustic method applied in the free acoustic field, which is very similar to the actual acoustic field at a workpost located near a noise source. This method also allows comparisons between various types of ear protectors (for example earmuffs and ear plugs). The 2nd experimental method, which gave much higher values than the actual attenuation values, is not recommended, whereas that of the "real ear", using white noise filtered into octave bands, is only useful for studying the sound damping efficacy of earmuffs.
Prace Centralnego instytutu ochrony pracy, 1973, Vol.23, No.78, p.245-259. 14 ref.

CIS 74-700 Plomp R., Mimpen A.M.
Comparative study of the sound attenuation provided by eight types of earplug
Vergelijkend onderzoek van de geluidverzwakking van acht typen oordopjes [en holandés]
The sound attenuation afforded by 8 different earplugs was determined at 500, 1,000, 2,000 and 4,000 Hz in 30 subjects. The results are presented in tabular and diagrammatic form and discussed. The average sound attenuation was between 14.5 and 27.8 dB.
Tijdschrift voor sociale geneeskunde, 31 Aug. 1973, Vol.51, No.17, p.576-581. Illus. 2 ref.

CIS 74-690 Townsend T.H., Bess F.H.
High frequency attenuation characteristics of ear protectors.
An experiment was carried out to evaluate different types of ear protector at 8, 10, 12, 14, 16 and 18 kHz. It was found that, with the possible exception of the custom-made earmould, good high-frequency protection is provided by all of the protectors evaluated. The advertised attenuation data for each protector showed less attenuation at 8 kHz than at 6 kHz, suggesting a trend towards less protection at the frequencies above 8 kHz. The results of this investigation revealed that such is not the case. Attenuation increased with frequency above 8 kHz, reaching a maximum at 14 kHz, but remaining fairly constant up to and including 18 kHz.
Journal of Occupational Medicine, Nov. 1973, Vol.15, No.11, p.888-891. Illus. 9 ref.

CIS 74-401 Waugh R.
dBA attenuation of ear protectors.
The adoption of hearing damage risk criteria expressed in A-weighted sound levels (dBA) and the consequent measurement of auditory hazards in dBA have made it necessary to measure dBA attenuation of hearing protective equipment. A study was therefore carried out to develop a method of calculating dBA attenuation of any continuous broad-band industrial noise when only the weighted sound levels of the noise are known. dBA attenuation of 30 hearing protectors was calculated in exposure to 619 industrial noise spectra. It was found that the same hearing protector may offer 20 dB more dBA attenuation to one noise than to another, but that noises of like C - A value (C-weighted value minus A-weighted value) are subject to approximately the same attenuation. 5 classes of C - A value are proposed and the average dBA attenuation values of each hearing protector for each noise class are calculated. With this information it is possible to select adequate ear protectors even though only the C-weighted and A-weighted sound levels of the noise are known.
Journal of the Acoustical Society of America, Feb. 1973, Vol.53, No.2, p.440-447. Illus. 14 ref.

CIS 74-111 Damongeot A., Lataye R., Tisserand M., Krawsky G.
Efficiency and comfort of personal hearing protectors
Efficacité et confort des protecteurs individuels contre le bruit. [en francés]
Results of tests carried out (for determining both comfort and efficiency) by the French National Research and Safety Institute (INRS) on 60 commercial models, and criteria for the choice of ear protectors in terms of noise characteristics and environmental requirements (protection against impact, speech communication). A selection of 12 ear protectors (1 helmet, 5 earmuffs, 6 earplugs) is presented in the form of diagrammatic data sheets.
Travail et sécurité, Sep. 1973, No.9, p.434-450. Illus. 2 ref.

1972

CIS 72-2710 Trynkowska D.
Methods of measuring the noise attenuation capacity of earmuffs
Metody pomiaru skuteczności tłumienia dźwięków przez nausznikowe ochronniki słuchu [en polonés]
The effectiveness of 3 models of earmuffs of Polish design was tested using the psycho-acoustic absolute hearing-threshold shift technique and objective "natural-ear" and "artificial-ear" methods. Statistical analysis showed the most suitable technique for this type of hearing protection device to be the psycho-acoustic technique using pure tones, and the "natural ear" using single-octave filtered white noise. The third of the above-mentioned techniques can be used for studying the infuence of such factors as type and thickness of the absorbent material employed, muff shape, etc.
Prace Centralnego instytutu ochrony pracy, 1972, Vol.22, No.73, p.63-82. Illus. 10 bibl.

1971

CIS 72-2714 Gasaway D.C.
Personal ear protection
Following a broad literature survey of the various aspects of hearing protection, the author discusses numerous methods used to evaluate the attenuation characteristics of ear protectors and considers additional features which influence the acceptance of certain types of protectors. The devices covered include earplugs, earmuffs, ear sockets, helmets, etc., to the exclusion of purely experimental devices. Attention has been paid in the report to the need for communication, the use of additional types of protective equipment and the requirements of comfort and wearability.
Report SAM-TR-71-13, School of Aerospace Medicine, Brooks Air Force Base, Texas 78235, USA, Aug. 1971. 143p. Illus. 186 bibl.

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