Perception of Lateral Misarticulation and Its Physical Correlates

In order to clarify the relationship between perceptual diagnosis of lateral misarticulation (LM) by sophisticated listeners and the physical correlates of LM, three experiments using sustained speech /∫/ were conducted. Experiment 1 was designed to compare the spectral envelopes of normal speech (NS) /∫/ with those of LM /∫/. Experiment 2 was designed to collect the auditory impressions of sophisticated listeners listening to LM and NS /∫/ with specific spectral envelope bands replaced by LM. These two experiments showed that: (1) the spectral envelopes of LM are flat or decrease along the frequency axis in the frequency band above approximately 4 kHz, and there is a substantial peak at around 3.2 kHz in LM, which varies peculiarly with time; (2) the replacement of the spectral envelope between 2.5 and 4.5 kHz of NS with that of LM resulted in a remarkable increase in auditory impressions of LM. The facts suggest that the spectral envelope characteristic of LM has a peculiar variation at around 3.2 kHz. Additionally, experiment 3 estimated the spectrum of sustained speech /∫/ using vocal tract area functions. The results suggest that typical peaks of LM are related to the length and position of the vocal tract constriction region.