Amplitude Distributions of Cochlear Microphonic Response to an Acoustic Sinusoid in Noise The distributions of instantaneous voltage amplitudes in the cochlear microphonic response recorded from a small segment along the basilar membrane are described by computing amplitude histograms. Comparisons are made between the distributions for noise and for those after the addition to the noise of successively stronger sinusoids. The amplitudes of ... Research Article
Research Article  |   March 01, 1968
Amplitude Distributions of Cochlear Microphonic Response to an Acoustic Sinusoid in Noise
 
Author Affiliations & Notes
  • Donald C. Teas
    University of Florida, Gainesville, Florida
  • Gretchen B. Henry
    University of Pittsburgh, Pittsburgh, Pennsylvania
Article Information
Hearing & Speech Perception / Acoustics / Research Articles
Research Article   |   March 01, 1968
Amplitude Distributions of Cochlear Microphonic Response to an Acoustic Sinusoid in Noise
Journal of Speech, Language, and Hearing Research, March 1968, Vol. 11, 63-76. doi:10.1044/jshr.1101.63
History: Received June 1, 1967
 
Journal of Speech, Language, and Hearing Research, March 1968, Vol. 11, 63-76. doi:10.1044/jshr.1101.63
History: Received June 1, 1967

The distributions of instantaneous voltage amplitudes in the cochlear microphonic response recorded from a small segment along the basilar membrane are described by computing amplitude histograms. Comparisons are made between the distributions for noise and for those after the addition to the noise of successively stronger sinusoids. The amplitudes of the cochlear microphonic response to 5000 Hz low-pass noise are normally distributed in both Turn I and Turn III of the guinea pig’s cochlea. The spectral composition of the microphonic from Turn I and from Turn III resembles the output of band-pass filters set at about 4000 Hz, and about 500 Hz, respectively. The normal distribution of cochlear microphonic amplitudes for noise is systematically altered by increasing the strength of the added sinusoid. A decrease of three percent in the number of small amplitude events (±1 standard deviation) in the cochlear microphonic from Turn III is seen when the rms voltage of a 500 Hz sinusoid is at −18 dB re the rms voltage of the noise (at the earphone). When the rms of the sinusoid and noise are equal, the decrease in small voltages is about 25%, but there is also an increase in the number of large voltage amplitudes. Histograms were also computed for the output of an electronic filter with a pass-band similar to Turn III of the cochlea. Strong 500 Hz sinusoids showed a greater proportion of large amplitudes in the filter output than in CMIII. The data are interpreted in terms of an anatomical substrate.

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