Previous work has demonstrated shorter ABR latencies in hearing-impaired listeners when compared with normal hearing listeners (Strelcyk et al., 2009).
The dynamic range between the threshold of hearing and loudness discomfort level is around 100 dB in normal hearing listeners.
Listeners with sensory hearing loss have raised hearing thresholds, but their loudness discomfort levels are essentially similar to those of normal hearing listeners.
Twenty-four normal hearing listeners audited the speech samples produced by the four speakers under the SC and SA conditions, three listeners in noise and three listeners in filtered listening conditions for each of the four speakers.
The subjective intelligibility tests were conducted on 28 Thai normal hearing listeners in four SNR levels (−6, −12, −18, and −24 dB) and subsequently on eight sensorineural hearing loss patients (with and without hearing aids) using clean stimuli.
While much benefit has been shown through bilateral implantation, patients who have bilateral cochlear implants (CIs) still do not perform as well as normal hearing listeners in sound localization and understanding speech in noisy environments.
These improvements should be grounded in a good understanding of the sensitivities of bilateral CI patients to the acoustic binaural cues that are important to normal hearing listeners for sound localization and speech in noise understanding.
The subjective evaluation of the proposed design with normal hearing listeners using comprehensibility listing test has been done and its performance has been compared to the existing state of the art research works.
The results suggested that patients' perceptual difficulty could be attributed to the nasality grouping, normally well separated for normal hearing listeners, shifting close to the glottals and aspirated obstruents.
The experimental results show that modulation filtering incorporated into a pre-processing algorithm improves intelligibility for normal hearing listeners when (1) the modulation filters are optimal for a specific reverberant condition (i.e., T60 = 1.1 s), and (2) consonants are preceded by highly powered segments.
The KLT algorithm was proved in [1] and [22] by subjective tests to perform well in terms of preserving speech intelligibility for normal hearing listeners and improving speech intelligibility significantly for cochlear implant users in regard to recognition of sentences corrupted by stationary noises, respectively.
