Critical Bands and Sensorineural Hearing Loss

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Abstract
Auditory frequency resolution is modelled in the critical-band concept. The width of the critical band (CB) denotes the bandwidth of frequency integration. This width is very hard to measure reliably. The slope of the CB indicate the power of frequency resolution of the ear. To measure the slope, wide-band noise signal can be used in which a certain band of frequencies is cut away by a so-called band-rejection filter. A tone is presented in the gap and its threshold is measured as a function of the bandwidth of the gap. This method has proven to be useful in clinical practics In many patients with sensorineural lesions (preception losses), the result were nearly normal. In other cases, the data would suggest that the critical-band mechanism is hardly functioning at all. A closer study was undertaken by measuring masking due to low- and high-frequency noise bands separately. Preliminary findings indicate that the low-frequency slope of the CB is in such cases nearly always normal, but the high-frequency side shows deviations. It is as if the pathological car under study has normal frequency analysis but it produces too many distortion components so that frequency resolution is affected on the high-frequency side only. Perhaps that is one of the main causes of these patients' difficulties in understanding speech in the presence of competing noise. The effect should, therefore, be considered in hearing-aid prescription

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