Accession Number : ADA138650

Title :   Evaluation of the Comprehension of Non-Continuous, Sped-Up Vocoded Speech: A Strategy for Coping with Fading HF (High Frequency) Channels.

Descriptive Note : Technical rept.,


Personal Author(s) : Lynch,J T ; Gold,B ; Tierney,J ; Bowers,C J

PDF Url : ADA138650

Report Date : 05 Jan 1984

Pagination or Media Count : 54

Abstract : A novel technique for coping with fading and burst noise on high frequency channels used for digital voice communication has been developed and evaluated. The technique transmits digital voice only during the high signal-to-noise ratio time intervals, i.e., channel on times, and speeds up the speech when necessary in order to avoid delays which would hinder conversation. The technique was evaluated using a model of the human speech comprehension process, which was tested using a spoken version of a reading comprehension test. The test involved fifteen spoken, two-minute paragraphs processed by a real-time channel vocoder simulation which had been modified to also simulate the on/off characteristics of a fading high frequency channel. Using a speed-up factor of 1.5, the percentage of correct test responses verified the comprehension model. If the average on time is longer than about two seconds or the average channel off time is shorter than about one-half second, then the speech is comprehensible. Since these conditions are met for most disturbed and undisturbed ionospheric conditions, it is concluded that the sped-up speech technique is appropriate for high frequency digital voice communication systems. (Author)

Descriptors :   *Speech transmission, *Reception, *Voice communications, *Vocoders, Digital communications, High frequency, Channels, Burst transmission, Noise(Radio), Ionosphere, Refraction, Data links, Models, Communication equipment, Perception, Comprehension, Strategy, Signal to noise ratio

Subject Categories : Voice Communications

Distribution Statement : APPROVED FOR PUBLIC RELEASE