Foreign Accent and Speech Distortion

Abstract

Speech distortion is defined as any operation that evokes inappropriate behavior by a listener in response to speech. Two categories of distorting operations are distinguished: (1) response-independent, in which the transfer function applied to the original speech signal is not determined by the probable response of the listener (e.g., masking, filtering); and (2) response-dependent, in which the distorting operation is related to the probable response of the listener during undistorted transmission and, therefore, may be specified in linguistic terms (e.g., foreign accent). Two experiments compare the effects of these 2 types of distortion. Twenty-four midwestern Americans listened to recorded articulation lists rendered by 1 American and 3 foreign-born speakers under 8 conditions of masking and filtering. Reducing the speech-to-noise ratio to 20 dB or the transmission bandwidth to 500 cps yields approximately 50% reduction in word articulation for both native- and foreign-accent speech. The latter was approximately 40% less intelligible than native speech under all experimental conditions. A “phonetic difference” measure of the degree of foreign accent holds promise as a predictor of the effects of accent on intelligibility; a significant correlation ratio of −0.66 was obtained.