Acoustic Alterations of Speech When Processed through Air Force Aircraft Communication Systems
Donald C. Gasaway · The Journal of the Acoustical Society of America · 1973
The acoustic composition of voiced speech signals received at a distance of 1 m (normal speech) is compared with those picked up by standard Air Force lip microphones that are transmitted via standard electroacoustic communication systems. The acoustic composition of speech used in Air Force ground and airborne operations is significantly different from that associated with normal live voice communication. Many voiced and voiceless speech components that constitute minimal acoustic amplitude in normal speaking situations undergo significant amplitude alterations when picked up by lip microphones. The author noted that pilots and other rated personnel frequently report that several transition flights are required before the speech communication messages are fully intelligible. This phenomenon has been studied and analyses of actual airborne speech communications are used to identify and define acoustic alterations that necessitate learning a new (or altered) type of speech. Voice prints of English vowels, diphthongs, and consonants are used to illustrate acoustic changes that exist between normal conversational speech and speech picked up by lip microphones. The results of this research suggest that the acoustic alterations created by picking up speech at the lips may increase intelligiblilty after the listener has learned how to process the signals accurately.