Effect of temporal modification and vowel context on speech perception in individuals with auditory neuropathy spectrum disorder (ANSD)

Abstract

Objectives: The study aimed to investigate the effect of time-scale modification on consonant perception in individuals with an auditory neuropathy spectrum disorder (ANSD). The study also evaluated the effect of vowel context on consonant perception. Study design: Eight individuals with ANSD in the age range of 15 to 24 years participated in the study. Their perception of eight stops and two liquids in the context of the vowels /a/, /i/ and /u/ were studied. The stimuli were stretched by 25%, 35% and 50% using pitch synchronous overlap and add algorithm. Results: It was found that 25% stretching resulted in significant improvement in perception in all three vowel contexts, while 35% stretching improved perception only in the context of /a/. However, 50% stretching resulted in deterioration in performance in all three vowel contexts. Furthermore, consonant perception in the context of /a/ and /u/ were significantly higher than that of /i/ in all the stretch conditions. Sequential information analysis revealed that perception of place and voicing were lowest in the context of /i/ compared to that of /a/ and /u/. Conclusion: Stretching the entire stimuli by a factor of 25% improves consonant perception in individuals with ANSD. In contrast, stretching beyond 25% resulted in either no improvement or deterioration in consonant perception. This information can be used to create a signal-processing algorithm that stretches the entire speech signal. Hence, without having to laboriously increase only the transition duration manually, improvement in speech perception can be brought about by stretching the whole signal. Additionally, consonant perception in individuals with ANSD is influenced by vowel context and hence two extreme vowels need to be used while studying the vowel context effect.