Effect of Syllabic and Dual Compression on Speech Identification Scores across Different Degrees of Hearing Loss

Abstract

The study aimed to investigate effects of compression types (syllabic and dual compression) on speech identification scores (SIS) in two conditions; Quiet condition at 40 dBHL and 70 dBHL of speech and, in the presence of noise (speech noise at 10 dB SNR) at same two intensities. The study was conducted on 20 subjects with sensori-neural hearing loss of various degrees (mild, moderate, moderately severe and severe). Speech identification scores were tested using phonemically balanced wordlist for Kannada speaking individuals developed by Yathiraj and Vijayalakshmi (2005). The results indicated that there was no significant difference in SIS obtained between syllabic and dual compression conditions, in quiet and in noise, at different input levels. Neither syllabic nor dual compression showed significant difference in SIS across different degrees of hearing loss. Higher presentation levels did not degrade the SIS, rather exhibited a better performance across different degrees of hearing loss, in both quiet and noisy conditions. Syllabic and Dual compression alone won't possibly help in improving speech perception as the former acts on the rapidly varying cues within a speech signal as it has short attack and release times whereas the latter adopts the time constant depending on the input signal. Hence, either syllabic or dual compression alone facilitates significant improvement in speech perception through hearing aids.