The Acoustic Stapedius Reflex in Relation to Critical Bandwidth

Abstract

The threshold of the acoustic stapedius reflex in man was investigated by means of changes in acoustic impedance of the ear. The contralateral ear was stimulated by using bands of noise and complex tones with various bandwidths. The experiments showed that the reflex threshold, expressed in decibels re 2.10 -5 N/m •', is almost constant for bandwidths less than a specific value and designated as "critical bandwidth." When the bandwidth was further increased, a decrease in the reflex threshold at approximately 3-6 dB/oct was observed. Assuming that the stapedius reflex mechanism is loudness governed in persons with normal hearing, these findings confirm the existence of a critical bandwidth in loudness summation. In addition, the findings indicate that the basis for the critical-band mechanism is located in the peripheral part of the auditory system, probably in the cochlea.

The effect of noise bandwidth on the contralateral suppression of transient evoked otoacoustic emissions

“…It has also been revealed that, for a given intensity, broadband noise will elicit a larger change in impedance than that associated with a pure tone (Block & Wightman, 1977;Flottorp, Djupesland, & Winther, 1971; 11 Margolis & Popelka, 1975). This implies that the AR is sensitive to a change in loudness that results from increasing the bandwidth of a stimulus maintained at a constant SPL.…”

“…Others have demonstrated that when stimuli such as pure tones and noise bands are matched for loudness, the magnitudes of the elicited acoustic reflexes are similar (Block et al, 1977;Gorga, Lilly, & Lenth, 1980). Some investigators have hypothesized that a critical band exists for the acoustic reflex (Flottorp et al, 1971).…”

“…Flottorp et al (1971) examined the relationship between critical bandwidth and the acoustic reflex. They found that for a given center frequency, the acoustic reflex threshold was constant until the bandwidth of the stimulus became wider than a value they designated as the critical reflex band (Flottorp et al, 1971). At this point, the reflex threshold decreased at a rate of approximately 3-6 dB per octave for center frequencies of 250, 500, 1000, 2000, and 4000 Hz (Flottorp et al, 1971).…”

“…Critical bands are thought to correspond to a constant distance of approximately 1.3 mm on the basilar membrane (Scharf, 1961). Flottorp et al (1971) examined the relationship between critical bandwidth and the acoustic reflex. They found that for a given center frequency, the acoustic reflex threshold was constant until the bandwidth of the stimulus became wider than a value they designated as the critical reflex band (Flottorp et al, 1971).…”

Impedance audiometry: Stapedial reflex eliciting conditions

“…If the extension of the band width is wider, there is no change up to the critical point. If the stimulating band width is continuously increased, there is a linear decrease of the re lex threshold [2,3,52], igure 3, he critical bandwidth is the width of the sound band in which suddenly there is changed some subjective hearing constants, mainly loudness, while the overall sound intensity stays constant.…”