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Subjective evaluation of a prototype earmuff exhibiting flat and nonlinear attenuation characteristics
J P Stokes1, L H Royster, R G Pearson
1International Business Machines Corporation Inc., Palo Alto, CA 94304.
American Industrial Hygiene Association Journal
|February 1, 1991
Summary
Police officers preferred new earmuffs for comfort, hearing protection, and speech clarity during firearms training. These earmuffs offered better performance, especially with quieter ammunition, enhancing communication in noisy environments.
Area of Science:
- Audiology
- Occupational Health
- Acoustics
Background:
- Firearms training generates high sound pressure levels (SPLs) posing risks to hearing.
- Conventional earmuffs may not provide optimal comfort or speech intelligibility in such environments.
- Developing advanced hearing protection is crucial for personnel in high-noise occupations.
Purpose of the Study:
- To evaluate subjective user responses to a novel earmuff with nonlinear attenuation characteristics.
- To compare the test earmuff against conventional earmuffs in a realistic firearms training scenario.
- To investigate the influence of ammunition type and noise exposure level on user preference.
Main Methods:
- Subjective user responses were collected from police officers during arms requalification.
- A counterbalanced crossover design was used, comparing a test earmuff with a conventional earmuff.
- Participants evaluated comfort, perceived hearing protection, and speech understanding.
Main Results:
- The test earmuff was significantly preferred for comfort, perceived hearing protection, and speech understanding.
- Nonlinear attenuation characteristics of the test earmuff improved noise reduction at higher SPLs.
- Quieter ammunition types correlated with significantly better speech understanding ratings for the test earmuff.
Conclusions:
- The test earmuff offers superior subjective performance compared to conventional earmuffs in firearms training.
- Level-dependent attenuation and ammunition type are key factors influencing user preference and communication effectiveness.
- Advanced earmuff designs can enhance both hearing protection and operational communication for law enforcement.
