Speech processing for the hearing-impaired: successes, failures, and implications for speech mechanisms

Abstract

People with sensorineural hearing impairment typically have more difficulty than normally hearing people in understanding speech in the presence of background sounds. This paper starts by quantifying the magnitude of the problem in various listening situations and with various types of background sound. It then considers some of the factors that contribute to this difficulty, including: reduced audibility; reduced frequency selectivity; loudness recruitment; and regions in the cochlea which have no surviving inner hair cells and/or neurones (dead regions). Methods of compensating for the effects of some of these factors are described and evaluated. Signal-processing methods to compensate for the effects of reduced frequency selectivity using the output of a single microphone have had only limited success, although methods using multiple microphones have worked well. Amplitude compression can compensate for some of the effects of loudness recruitment, allowing speech to be understood over a wide range of sound levels. The exact form of the compression (fast-acting versus slow-acting, single-channel versus multiple channel) does not seem to be critical, suggesting that the relative loudness of different components of speech, and dynamic aspects of loudness perception do not need to be restored to ''normal''.

Speech Enhancement in Hearing Aids Using Conjugate Symmetry of DFT and SNR-Perception Models

“…The unprocessed magnitude is combined with modified phase during synthesis. This results into cancellation of low energy (noise) components more than high energy (speech) components [3,14,15]. This leads to enhancement of speech and is comparable with existing algorithms used in hearing aids.…”

Neural and Cognitive Effects of Hearing Loss on Speech Processing

“…Besides noise exposure and genetic predisposition, age-related changes in the auditory system (presbycusis) also contribute to the development of sensorineural hearing loss (Humes et al, 2012) 1 . Sensorineural hearing loss, hereon denoted only hearing loss, causes several changes in the auditory system (for review, see Moore, 2003). The most prominent changes are (1) reduced audibility resulting from raised audiometric thresholds.…”

“…As the level at which sounds become uncomfortably loud generally remains unchanged, the raised audiometric thresholds often result in (2) a lower dynamic range (Steinberg & Gardner 1937, see Figure 1). The frequency-specificity of the cochlea decreases due to broadening of the auditory filters, reducing the (3) spectral and (4) temporal precision of sound encoding (Moore, 2003). In combination, the lowered spectral and temporal precision cause a reduced sensitivity towards the rapid oscillations within auditory signals, i.e., the temporal-fine structure (Lorenzi et al, 2006;Moore, 2008).…”

Benefício do sistema de frequência modulada em crianças usuárias de aparelhos de amplificação sonora individual e implante coclear

“…Diversos estudos apontam que pessoas com deficiência auditiva sensorioneural apresentam maiores dificuldades em compreender a fala em ambientes ruidosos, em comparação a indivíduos com limiares auditivos dentro dos padrões de normalidade (Killion 1997a(Killion ,1997bMc Farland, 2003;Moore, 2003;Lewis et al, 2004;Luts et al, 2004;Henrique et al, 2008).…”

“…Portanto, para desenvolver um ambiente onde a aprendizagem possa ocorrer, as salas de aula precisam de gerenciamento acústico e uma favorável relação S/R (Flexer 2003b (Moore, 2003).…”