Distortion product otoacoustic emission (DPOAE) levels in response to primary pairs (f2 = 2 or 4 kHz, L2 ranging from 20 to 60 dB SPL, L1=0.4L2+39dB) were measured with and without suppressor tones (f3), which varied from 1 octave below to 1/2 octave above f2, in normal-hearing subjects. Suppressor level (L3) varied from-5 to 85 dB SPL. DPOAE levels were converted into decrements by subtracting the level in the presence of the suppressor from the level in the absence of a suppressor. DPOAE decrement vs L3 functions showed steeper slopes when f3<f2 and shallower slopes when f3>f2. This pattern is similar to other measurements of response growth, such as direct measures of basilar-membrane motion, single-unit rate-level functions, suppression of basilar-membrane motion, and discharge-rate suppression from lower animals. As L2 increased, the L3 necessary to maintain 3 dB of suppression increased at a rate of about 1 dB/dB when f3 was approximately equal to f2, but increased more slowly when f3<f2. Functions relating L3 to L2 in order to maintain a constant 3-dB reduction in DPOAE level were compared for f3<f2 and for f3≅f2 in order to derive an estimate related to "cochlear-amplifier gain." These results were consistent with the view that "cochlear gain" is greater at lower input levels, decreasing as level increases.
ASJC Scopus subject areas
- Arts and Humanities (miscellaneous)
- Acoustics and Ultrasonics