Effects of spectral smearing on the intelligibility of sentences in noise

Abstract

Cochlear hearing loss is generally associated with a variety of deficits in the ability to analyze sounds, including reduced frequency selectivity. The complex interrelationships between the different deficits have made it difficult to assess the contribution of reduced frequency selectivity to the difficulties experienced by hearing-impaired people in understanding speech. To address this question, the effects of reduced frequency selectivity on the place representation of speech stimuli in the auditory system were simulated by "smearing" the spectra of the stimuli, using the overlap-add method. The smearing was designed to evoke excitation patterns in a normal ear that would resemble those evoked in an impaired ear using unsmeared stimuli. Several different types of smearing were used, simulating specific degrees of broadening and asymmetry of the auditory filter. Sentences in quiet and in speech-shaped noise were smeared and presented to normally hearing listeners in intelligibility tests. The results showed that the intelligibility of speech in quiet was hardly affected by spectral smearing, even for smearing that simulated auditory filters six times broader than normal. However, the intelligibility of speech in noise was adversely affected by the smearing, especially for large degrees of smearing and at a low speech-to-noise ratio (-3 dB). Simulation of asymmetrical broadening of the lower side of the auditory filter had a greater effect than simulation of asymmetrical broadening of the upper side, suggesting that upward spread of masking may be particularly important.

Temporal-Envelope Reconstruction for Hearing-Impaired Listeners

“…The main deleterious effects of cochlear damage on the intelligibility of 3-band FM speech sounds would then correspond to (1) a reduction in the number of independent peripheral channels which transmit envelope information (see also Swaminathan and Heinz 2011) and (2) a reduction in the ability to discriminate and use envelope information for speech identification. Previous studies demonstrated that speech intelligibility in quiet is not affected by a reduction in frequency resolution by a factor of 2-4 (e.g., Baer and Moore 1993;Shannon et al 1995;Baskent 2006). Other studies indicated that HI listeners may show poorer-than-normal AM discrimination abilities (Grant et al 1998;Buss et al 2004).…”

Effects of low-pass filtering on intelligibility of periodically interrupted speech

“…Thus, we could eliminate other factors relevant to hearing impairment, such as the suprathreshold deficits or age-related cognitive decline. A more deleterious effect of the combination of two distortions, e.g., spectral smearing and background noise, as compared with sole distortion, e.g., spectral smearing, is known (Baer and Moore, 1993). Similarly, the combined effect of suprathreshold auditory deficits and periodic interruptions is known to be detrimental to speech intelligibility, e.g., amplitude modulation and frequency modulation filtering and interruptions (Gnansia et al, 2010;Nelson and Jin, 2004;Gilbert et al, 2007).…”

An analysis of the effects of electrical field interaction with an acoustic model of cochlear implants

“…In two representative simulations of spectral smearing, widened noise bands (Boothroyd et al, 1996) and a smearing matrix (Baer and Moore, 1993) were used to smear the spectrum of the original speech signal. Both approaches aimed to simulate the widened auditory filters typical of CI users.…”