Real ear attenuation at threshold for three audiometric headphone devices: implications for maximum permissible ambient noise level standards.
Franks-JR; Engel-DP III; Themann-CL
Ear Hear 1992 Feb; 13(1):2-10
A study of real ear attenuation at threshold (REAT) obtainable for three audiometric headphone devices was conducted. Fourteen volunteers, seven males, 20 to 44 years old, with normal hearing were fitted with a standard Telephonics headset containing TDH-50P earphones and a model 51 cushion only or the model 51 cushion enclosed in Amplivox Audiocups headphone or Peltor AudioMate headphone enclosures. REATS were measured using 0.333 octave band noise signals over the range 125 to 8000 hertz (Hz) according to the American National Standards Institute (ANSI) method S12.6-1984. Overall subjects and test sessions the AudioMate demonstrated the highest attenuation and the model 51 cushion alone the least attenuation. The REATs of the Audiocups approximated those of the model 51 cushion through 500Hz and those of the AudioMate at frequencies of 1000Hz or higher. All three devices tended to show increasing REATs with increasing frequency. The model 51 cushion and Audiocups provided maximum attenuation at 4000Hz. The Audiomate showed a small increase in attenuation at 8000Hz. The authors conclude that the REATS for the model 51 cushion compare favorably with measured in a previous study and in previous studies of an acoustically equivalent cushion, the MX-41/AR. Estimates of the threshold shifts made from the data indicate that the model 51 cushion alone is insufficient to attenuate the levels of background noise permitted under the ANSI 53.1-1977 standard. Only the Audiomate provides the attenuation necessary to permit threshold testing down to 0 decibels with less than a 1 decibel threshold elevation.
NIOSH-Author; Ear-protectors; Audiometry; Laboratory-techniques; Equipment-reliability; Laboratory-testing; Hearing-threshold; Equipment-design
Ear and Hearing