FEMALE VOICE COMMUNICATIONS IN HIGH-LEVELS OF AIRCRAFT COCKPIT NOISES- PART 1 - SPECTRA, LEVELS, AND MICROPHONES

Hypothesis: Female produced speech, although more intelligible than ma le speech in some noise spectra, may be more vulnerable to degradation by high levels of some military aircraft cockpit noises. The acoustic features of female speech are higher in frequency, lower in power, an d appear more susceptible than male speech to masking by some of these military noises. Current military aircraft voice communication system s were optimized for the male voice and may not adequately accommodate the female voice in these high level noises. Methods: This applied st udy investigated the intelligibility of female and male speech produce d in the noise spectra of four military aircraft cockpits at levels ra nging from 95 dB to 115 dB. The experimental subjects used standard fl ight helmets and headsets, noise-canceling microphones, and military a ircraft voice communications systems during the measurements. Results: The intelligibility of female speech was lower than that of male spee ch for all experimental conditions; however, differences were small an d insignificant except at the highest levels of the cockpit noises. In telligibility for both genders varied with aircraft noise spectrum and level. Speech intelligibility of both genders was acceptable during n ormal cruise noises of all four aircraft, but improvements are require d in the higher levels of noise created during aircraft maximum operat ing conditions. Conclusions: The intelligibility of female speech was unacceptable at the highest measured noise level of 115 dB and may con stitute a problem for other military aviators. The intelligibility deg radation due to the noise can be neutralized by use of an available, i mproved noise-canceling microphone, by the application of current acti ve noise reduction technology to the personal communication equipment, and by the development of a voice communications system to accomodate the speech produced by both female and male aviators.