A Perceptual Study of CV Syllables in both Spoken and Whistled Speech: a Tashlhiyt Berber Perspective

The present study compares the perceptual categorization of four CV syllables /ta, da, ka, ga/ in two different speech registers - modal speech and whistled speech - of Tashlhiyt Berber used in the Moroccan High Atlas. Whistled speech in a non-tonal language such as Tashlhiyt is a special speech register used for long distance dialogues that consists of the natural production of vocalic and consonantal qualities in a simple modulated whistled signal. The technique of whistling imposes various restrictions on speech articulation, which result in a simplification of the phonetics of spoken speech into a `whistled formant'. Here, we describe this simplification for Tashlhiyt syllables /ta, da, ka, ga/ and use them as stimuli in a behavioral experiment. We analyze and compare the perceptual categorization obtained from native Tashlhiyt listeners (trained since childhood in whistled speech) for both speech registers on these 4 syllable types. Results show that whistled stimuli were fairly well identified (similar to 42%) above chance (25%), though less well than spoken ones (similar to 84%). The detailed analysis of confusions between CVs enabled us to understand better how whistled consonants are perceived, highlighting the phonological contrasts that are best perceived and retained from spoken to whistled speech in this language.