NOISE ATTENUATION CHARACTERISTICS OF FOUR ANTI-BUFFET HELMETS AND AN INSERT TYPE EAR PLUG.
Abstract
Four prototype anti-buffet helmets, General Textile H-5-3, having special earphone cushions incorporated into them and a Dunbar-Knight Hearing Guard, insert type ear plug, were evaluated concerning their noise-tone-speech attenuation characteristics. Due to the construction of both type devices, physical measures (detailed in Joint Project Report NM 001 064.01.16) were not obtainable from the artificial ear enclosed within the plaster 'dummy' head. The limitation imposed by the lack of helmet head size ranges did not allow a full listener-observer panel to contribute to the mean attenuation values. The available personnel who 'fit' the helmets were five. These five individuals made judgments on three listening tasks which included (a) pulsed discrete frequency relative threshold shifts, (b) pulsed wide-band and octave-bands of noise relative threshold shifts, and (c) Spondee word reception relative threshold shifts. The listening observations were made under binaural, free-field conditions. None of the present devices attenuate as well as several types tested earlier, particularly in the lower end of the audible spectrum. The attenuation characteristics are probably not dissimilar to the V-51R ear warden for frequencies above 2000 cps or for octave band noise above the 600 - 1200 cps range. Two of the Gen. Tex. helmets, No. 2 and 4, attenuated Spondee words as well as the V-51R ear warden. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 05, 1956
- Accession Number
- AD0622057
Entities
People
- Gilbert C. Tolhurst
Organizations
- Ohio State University