On the Relation between the Acoustic Reflex and Loudness

Abstract

For each of four subjects, a set of equal-loudness contours constructed from obtained loudness balances was compared to contours of contra- or ipsilateral sinusoidal stimulations that activate the acoustic reflex to the same degree, as indicated by a constant change in acoustic impedance at the eardrum. Two subjects produced “normal” equal-loudness contours, showing close coincidence with the respective equal-reflex contours; the remaining two subjects produced “abnormal” equal-loudness contours, exhibiting significant departures from the respective equal-reflex contours. Results indicate no systematic difference in the sensitivity of the acoustic reflex to ipsi- and to contralateral stimulation. Middle-ear attenuations calculated from the magnitude of the acoustic impedance at the eardrum, together with estimates of the reflex-generated attenuations, were employed to transform the sound-pressure levels (SPL's) of the equal-reflex contours to relative values of volume velocity of the cochlear fluid. The transformed contours support the hypothesis that the acoustic reflex is activated to the same degree by sinusoidal stimulations producing the same total number of neural impulses within about 200 msec. For some subjects, equality of loudness between two sinusoidal stimulations appears to be attained under this same condition.

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

“…Similar results were reported by Deutsch (1972) and Margolis and Popelka (1975). Others have reported that when stimuli are matched for loudness, acoustic reflex magnitudes are similar, which suggests that the acoustic reflex responds to loudness (Block et al, 1977;Gorga et al, 1980;Margolis & Popelka, 1975;Ross, 1968). The effect is seen regardless of whether reflexes were elicited contralaterally or ipsilaterally (Ross, 1968).…”

“…The similarities between these two systems have been described. The AR is responsive to changes in loudness (Block et al, 1977;Gorga et al, 1980;Margolis & Popelka, 1975;Ross, 1968). It is not known whether the same is true for MOC effects.…”

“…Others have reported that when stimuli are matched for loudness, acoustic reflex magnitudes are similar, which suggests that the acoustic reflex responds to loudness (Block et al, 1977;Gorga et al, 1980;Margolis & Popelka, 1975;Ross, 1968). The effect is seen regardless of whether reflexes were elicited contralaterally or ipsilaterally (Ross, 1968). Norman and Thornton (1993) examined contralateral suppression of TEOAEs in humans related to critical bandwidth.…”

Loudness Enhancement Following Contralateral Stimulation

“…Perceived loudness is reduced, for instance, by. factors such as noise-induced hearing loss (yon B•k•sy, 1960) or contraction of the middle ear muscles (Ross, 1968). It may also be increased in several situations to be discussed separately later.…”

Magnitude of the acoustic reflex for either homophasic (0°) or antiphasic (180°) binaural activating signals presented in a background of noise

“…A number of studies have been conducted that address this issue directly. Some of these experiments suggest that no relation exists between the two measures (Margolis and Popelka, 1975;Scharf, 1976), whereas others indicate that some relation exists between loudness and the acoustic reflex (Ross, 1968;Block and Wightman, 1977;Block and Wiley, 1979;Gorga, Lilly, and I, enth, 1979 …”