The Preference of Slope Overload to Granularity in the Delta Modulation of Speech

Vol. SO, No. 10, December, 1971 Printed in U.S.A. The Preference of Slope Overload to Granularity in the Delta Modulation of By N. S. JAYANT and A. E. R O S E N B E R G ( M a n u s c r i p t r e c e i v e d J u n e 18, 1 9 7 1 ) A preference study was made to assess the relative annoyance values of slope-overload distortion and granular noise in delta-modulated speech. A recently described adaptive delta modulator was simulated at frequencies of 20 and 40 kHz, and controlled amounts of the two types of degradation were introduced into samples of a 2-second utterance. Rankings were obtained for these samples on the basis of preference judgments of nine listeners, each of whom assessed the samples, pairwise, in a townamenttype strategy. Residts indicate that the speech sample exhibiting the minimum degradation on an objective, overall-noise-power basis is not subjectively the most preferred sample. Furthermore, the subjectively optimum delta modulator exhibits greater overload and lesser granularity than the objectively optimum device.