Office of Aerospace Medicine Technical Reports
FAA Office of Aerospace Medicine
Civil Aerospace Medical Institute
Report No: DOT/FAA/AM-70/6
Title and Subtitle: Auditory processing for speech intelligibility improvement
Report Date: April 1970
Authors: Tobias JV
Abstract: Pilots of light aircraft often seem to prefer loudspeakers to earphones even though covering the ears helps most of them to improve the signal-to-noise ratio of speech transmissions, and to decrease the pilot's exposure to fatiguing noise. The auditory-fatigue problem can be handled by pilot education; the problem of deteriorating signal-to-noise ratios, though, can be approached not just by putting earphones on fliers but also by applying to the loudspeaker situation some of the theoretical principles that have led to techniques of apparent signal-level improvement and real speech-intelligibility improvement under earphones.
The human auditory system, appropriately stimulated, is capable of creating the effect of an improved signal-to-noise ratio without actually changing either the signal or the noise intensities. Tests of these techniques show that their proper application to a loudspeaker-listening situation is equivalent to a 5-dB improvement in signal-to-noise ratio. Since the method is based in the human observer's signal-processing ability, it requires no special equipment in the aircraft. Two loudspeakers are used, driven from the same signal source, but with the two speakers wired in opposite phase to each other.
Within broad limits, variations in speaker placement permit the improved results. These limits are defined.
Key Words: Noise
No. of Pages: 10
Civil Aerospace Medical Institute
Report No: DOT/FAA/AM-70/6
Title and Subtitle: Auditory processing for speech intelligibility improvement
Report Date: April 1970
Authors: Tobias JV
Abstract: Pilots of light aircraft often seem to prefer loudspeakers to earphones even though covering the ears helps most of them to improve the signal-to-noise ratio of speech transmissions, and to decrease the pilot's exposure to fatiguing noise. The auditory-fatigue problem can be handled by pilot education; the problem of deteriorating signal-to-noise ratios, though, can be approached not just by putting earphones on fliers but also by applying to the loudspeaker situation some of the theoretical principles that have led to techniques of apparent signal-level improvement and real speech-intelligibility improvement under earphones.
The human auditory system, appropriately stimulated, is capable of creating the effect of an improved signal-to-noise ratio without actually changing either the signal or the noise intensities. Tests of these techniques show that their proper application to a loudspeaker-listening situation is equivalent to a 5-dB improvement in signal-to-noise ratio. Since the method is based in the human observer's signal-processing ability, it requires no special equipment in the aircraft. Two loudspeakers are used, driven from the same signal source, but with the two speakers wired in opposite phase to each other.
Within broad limits, variations in speaker placement permit the improved results. These limits are defined.
Key Words: Noise
No. of Pages: 10
Last updated: Friday, June 1, 2012