Measurement of distortion product phase in the ear canal of the cat
作者:
P. F. Fahey,
Jont B. Allen,
期刊:
The Journal of the Acoustical Society of America
(AIP Available online 1997)
卷期:
Volume 102,
issue 5
页码: 2880-2891
ISSN:0001-4966
年代: 1997
DOI:10.1121/1.420343
出版商: Acoustical Society of America
数据来源: AIP
摘要:
Amplitudes of odd order distortion products (DPs) that are detected in animal ear canals have been used to probe cochlear health, to search for cochlear amplification, and to measure aspects of cochlear mechanical frequency response. Like the DP amplitude, DP phase is also an important measure of the cochlear mechanical response. Reported here are measurements of DP phase in the ear canal of the cat. The phase data show frequency-dependent time delays. One of these delays is a function off2,the frequency of the higher-frequency primary. Hence the DP phaseφdis of the formφd=φ0+ωdτ,whereωdis the DP angular frequency and τ is a fixed time delay. Our results show thatφdis independent of input levela2as long as the ratioa2/a1⩽2,wherea2anda1are the amplitudes of the input tones. Asa2/a1becomes greater than two, the fixed time delays increase for DPs whose frequencies are less than the frequencies of the input tones. When both levels are varied together the delay increases as the levels decrease. There can be phase changes as large as π associated with deep nulls in the DP magnitude for the two lower-frequency DPs. Features of the nulls may be modeled assuming that there is partial reflection of the DP wave from the DP place. The assumption of energy reemitted from the DP place also explains amplitude-ratio-dependent time delays and 2π level-dependent bifurcations in phase. The DP phase shows different dependencies forf22 kHz.
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