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Sound pressure gain produced by the human middle ear
1Division of Otolaryngology/Head and Neck Surgery, Stanford University, School of Medicine, CA 94305, USA.
Summary
This study measured human middle ear pressure gain, finding significant gain at lower frequencies peaking near 0.9 kHz. Individual differences were linked to tympanic membrane function, not cochlear impedance.
Area of Science:
- Otoacoustic Emissions
- Auditory Physiology
- Biomedical Engineering
Background:
- The middle ear's acoustic function is crucial for impedance matching between air and cochlear fluid.
- Limited data exists on human middle ear pressure gain, essential for understanding hearing.
- This study addresses this gap by quantifying middle ear pressure gain in human temporal bones.
Purpose of the Study:
- To experimentally determine the middle ear pressure gain in human subjects.
- To investigate the frequency-dependent characteristics of middle ear pressure gain.
- To explore factors contributing to individual variations in middle ear pressure gain.
Main Methods:
- Experiments were conducted on six fresh human temporal bones.
- Stapes footplate displacement and phase were measured using laser Doppler vibrometry.
- Tympanic membrane, malleus, and incus were sequentially removed, with umbo displacement measured initially.
Main Results:
- The middle ear exhibits major gain at lower frequencies, with a peak gain of 26.6 dB near 0.9 kHz.
- Below 1.0 kHz, the mean gain was 23.0 dB; above 1.0 kHz, gain decreased at -8.6 dB/octave.
- Significant individual differences in pressure gain were observed, correlating with tympanic membrane function.
Conclusions:
- The human middle ear provides substantial pressure gain, particularly at lower frequencies.
- Tympanic membrane characteristics significantly influence middle ear pressure gain.
- Cochlear impedance does not appear to be a primary factor in individual variations of middle ear gain.