The effect of perceived sound quality of speech in noisy speech perception by normal hearing and hearing impaired listeners

Most noise reduction algorithms in current assistive hearing devices were designed to reduce noise to achieve the best signal to noise ratio (SNR) possible, presuming that the perceived quality of speech can be compromised as long as the level of noise is relatively much lower than the level of speech. In this study, we investigated and compared various factors other than SNR that may possibly affect the quality rating pattern of normal hearing (NH), cochlear implant (CI) and hearing aid (HA) subjects. In one of the comparisons, we found that the perceived sound quality ratings of noisy sentences at the same SNR were dependent on the level of speech present in the sentences rather than the noise. Noisy sentences with a higher level of speech were rated higher in perceived sound quality by NH subjects. However, in a similar comparison, CI subjects rated higher in perceived sound quality when the level of speech present was lower, but HA subjects do not show any clear trend with their perceived sound quality ratings on the same sentences.