Subjective evaluation of a prototype earmuff exhibiting flat and nonlinear attenuation characteristics.
Stokes-JP; Royster-LH; Pearson-RG; Royster-JD
Am Ind Hyg Assoc J 1991 Feb; 52(2):52-60
A study of subjective user responses to a prototype earmuff containing a cartridge mechanism within each cup was conducted. The earmuff exhibited nonlinear attenuation that increased with increasing sound level at sound pressure levels (SPLs) greater than 120 decibels (dB) and flat attenuation of about 25dB over the frequency range 500 to 8000 hertz at SPLs below 120dB. The cohort consisted of 139 police officers, 128 males, median age 25 years, from Raleigh, North Carolina. The subjects wore the prototype earmuff or a comparable conventional earmuff alternately during two handgun requalification trials at an outdoor firing range. Subjects used one of two types of ammunition, special jacketed hollow point (JHP) or semiwadcutter (WAD) bullets. The JHP and WAD bullets produced A-weighted peak SPLs of 156 and 154dB, respectively, when fired. After each firing test the subjects completed a questionnaire to obtain their opinions on comfort, perceived hearing protection, and speech understanding. The subjects rated the prototype earmuff better in terms of comfort, perceived hearing protection, and speech understanding than the conventional earmuff. When the WAD ammunition was used the prototype earmuff was rated significantly better in all categories. Users of JHP ammunition rated the prototype significantly better with respect to comfort and speech. Subjects with preexisting high frequency hearing loss significantly preferred the prototype earmuff with regard to speech understanding. The authors conclude that the prototype earmuff appears to offer a special advantage to those with high frequency hearing loss.
NIOSH-Publication; NIOSH-Grant; Training; Impulse-noise; Hearing-protection; Law-enforcement-workers; Psychophysiology; Noise-exposure; Questionnaires; Equipment-design; Equipment-reliability; Statistical-analysis; Hearing-loss
Environmental Sciences & Engr Univ of North Carolina Sch of Public Health 201 H Chapel Hill, N C 27514
American Industrial Hygiene Association Journal
University of North Carolina Chapel Hill, Chapel Hill, North Carolina