Hearing Protection

ABSTRACT

Hearing protectors, unless specifically designed, attenuate the higher frequency sound energy more than lower frequency energy. Because such a nonuniform attenuation characteristic can be less than optimal for certain high-fidelity requirements, acoustically tuned hearing protectors were developed. These include the ER-15 and the ER-25 earplugs that-as the name suggests-provide a uniform attenuation of 15 dB and 25 dB, respectively. To obtain different attenuation characteristics, modifications of these earplugs are clinically possible, but they will lose their uniform attenuation property. Such earplugs can be used in the performing arts and in industrial settings with noise levels below 100 dBA. The ER-20 (or HI-FI earplug) noncustom earplug also is available. Objective techniques, such as microphone-in-real-ear (MIRE) and the use of acoustical test fixtures (ATF), and subjective techniques, such as real ear attenuation thresholds (REAT), are two valid methods for assessing the effects of hearing protection. Regardless of the technique, the resulting data can be expressed in a single number rating scheme such as the Noise Reduction Rating (NRR).

KEYWORDS

Attenuation - hearing protector - ER-15 - NRR - noise

REFERENCES

• 1 Zwislocki J. Acoustic attenuation between the ears.  J Acoust Soc Am . 1953;  25 752-759
• 2 Zwislocki J. In search of the bone-conduction threshold in a free sound field.  J Acoust Soc Am . 1957;  29 795-804
• 3 Shaw E, Theissen G. Improved cushion for ear defenders.  J Acoust Soc Am . 1958;  30 24-36
• 4 Shaw E, Theissen G. Acoustics of circumaural earphones.  J Acoust Soc Am . 1962;  34 1233-1243
• 5 Berger E. Methods of measuring the attenuation of hearing protection devices.  J Acoust Soc Am . 1986;  6 1655-1687
• 6 Schroeter J. The use of acoustical test fixtures for the measurement of hearing protector attenuation. Part I: review of previous work and the design of an improved test fixture.  J Acoust Soc Am . 1986;  79 1065-1081
• 7 Berger E, Kerivan J. Influence of physiological noise and the occlusion effect on the measurement of real-ear attenuation at threshold.  J Acoust Soc Am . 1983;  1 81-94
• 8 Berger H. Tips for Fitting Hearing Protectors.  E.A.R.LOG 19. Indianapolis, IN: Cabot Safety Corp; 1988
• 9 Abel S, Alberti P, Haythornwaite C, Riko K. Speech intelligibility in noise with and without ear protectors. In: Alberti PW, ed. Personal Hearing Protection in Industry New York: Raven Press 1982: 371-386
• 10 Killion M, DeVilbiss, Stewart J. An earplug with uniform 15-dB attenuation.  Hear J . 1988;  5 14-16
• 11 Chasin M. The acoustic advantages of CIC hearing aids.  Hear J . 1994;  11 13-17
• 12 Killion M, Stewart J, Falco R, Berger E. Improved audibility earplug. U.S. Patent 5,113,967; 1992
• 13 Gauthier E, Burak M. Towards a high fidelity hearing aid: The folded horn.  Hear Aid J . 1983;  10 37-39
• 14 Chasin M, Chong J. Localization problems with modified and non-modified ER-15 Musician's Earplugs.  Hear J . 1999;  2
• 15 Chasin M, Chong J. A clinically efficient hearing protection program for musicians.  Med Probl Perform Art . 1992;  7 40-43
• 16 Chasin M. Musicians and the Prevention of Hearing Loss.  San Diego, CA: Singular; 1996
• 17 Killion M. The parvum bonum, plus melius fallacy in earplug selection. In: Beilin L, Jensen GR, eds. Recent Developments in Hearing Instrument Technology (15th Danavox Symposium) Kolding, Denmark: Scanticon 1993: 415-433
• 18 Berger E. Can Hearing Aids Provide Hearing Protection?. E.A.R.LOG 18 Indianapolis, IN: Cabot Safety Corp; 1987
• 19 Hetu R, Tran Quoc H, Tougas Y. Can an inactivated hearing aid act as a hearing protector?.  Can Acoustics . 1992;  3 35-36
• 20 Alberti P. Personal Hearing Protection in Industry.  New York: Raven Press; 1982
• 21 Behar A, Desormeaux J. NRR, ABC or .  . . Canadian Acoustics . 1994;  1 27-30
• 22 Botsford J. How to estimate dBA reduction of ear protectors.  Journal of Sound Vibration . 1973;  6 32-33
• 23 Preves D, Pehringer J. Calculating individuals NRRs in situ using subminiature probe microphones.  Hear Instrum . 1983;  3 10-14
• 24 Johnson D, Nixon C. Simplified methods for estimating hearing protector performance.  Journal of Sound Vibration . 1974;  7 20-27