Naval Underwater Sound Laboratory Naval Submarine Medical Center
نویسندگان
چکیده
The reception of speech transmitted through an acoustic channel such as the ocean is limited by multipath "time-smearing." The purpose of this study was to obtain a quantitative measure of the effects of such timesmearing on speech intelligibility. A linear, time-invariant channel was used as a model of the ocean. The impulse response of this channel was a sample of band-limited Gaussian noise. Using Fast Fourier Transform techniques, words of the Modified Rhyme Test were convolved with, or smeared in the time domain, by this channel impulse response. The intelligibility of these "smeared" words was measured as a function of the impulse response duration, T. Intelligibility decreased monotonically to about 75 percent as T increased to 200 milliseconds. Further increase in T did not significantly lower intelligibility. Distortions in time evaluated herein did not impose serious limitations to the reception of short words. However, a detailed analysis of consonantal errors revealed that sounds occurring in the middle of a word are much harder to hear correctly than are sounds at the beginning or ending of an utterance. We conclude that timesmearing will more seriously interfere with the intelligibility of connected or conversational speech. SPEECH INTELLIGIBILITY IN A STATIONARY MULTIPATH CHANNEL
منابع مشابه
Naval Submarine Medical Research Laboratory Naval Submarine Medical Center Groton, Connecticut 06340 Memorandum. Report 70-7 an Investigation of the Effects of a Helium-oxygen Breathing Mixture on Hearing in Naval Personnel
Hearing levels of three subjects were measured at 125, 1000 and 8000 Hertz while the subjects were breathing air and while breathing an 80%/20% mixture of helium and oxygen. No significant change in hearing levels which could be attributed to the effects of the gas breathed were detected during or following a thirty-minute period on helium-oxygen.
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The visual tasks aboard submarines can be analyzed according to the demand for visual acuity placed upon the men performing them. Such assessments have been made on several occasions in the past, in response to increasing shortages of manpower, and have often resulted in relaxation of standards. These studies are summarized, the rationale for current standards stated and other solutions to the ...
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1Research Department for Underwater Acoustics and Marine Geophysics, Bundeswehr Technical Centre for Ships and Naval Weapons, Naval Technology and Research (WTD 71), Klausdorfer Weg 2, 24148 Kiel, Germany 2Navy Center for Applied Research in Artificial Intelligence, Naval Research Laboratory, 4555 Overlook Avenue S.W., Washington, DC 20375, USA 3Acoustic Research Laboratory, National University...
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تاریخ انتشار 2014