Issue N# 3 - 2003
Time-intensity trade of bilaterally bone-conducted sounds in normal hearing subjects.
Authors : S. Schmerber, K. Sheykholeslami, M. H. Kermany, S. Hotta, K. Kaga (Grenoble, Tokyo)
Ref. : Rev Laryngol Otol Rhinol. 2003;124,3:179-185.
Article published in english
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Objective and methods: in an effort to examine the rules by which information of bilaterally applied bone-conducted signals arising from interaural time differences (ITD) and interaural intensity differences (IID) is combined, data were measured for continuous 500 Hz narrow-band noise at 60 dBHL in 30 normal-hearing subjects using a centering method. Time-intensity trading functions were obtained by means of a sound image shifted towards one side by presenting an ITD, and shifted back to a centered sound image by varying the IID in the same ear. ITD values were varied from -600 to +600 µs at 200 µs steps, where negative values indicate delays to the right ear. Results: time-intensity trading functions in response to bone-conducted signals showed significantly lower discrimination thresholds across IIDs, when compared to a control group with applied air-conducted signals. These findings can be interpreted as a constructive interference effect related to the intimate mechanism of bilateral bone conduction, where interaural time differences play a major role. Conclusion: time-intensity trade of bilaterally bone-conducted sounds in normal-hearing subjects is the highly sensitive. The high speed of sound through the skull may be the main reason for the high sensitivity of time-intensity trading.
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