Acoustic Neuromas and the Acoustic Impedance of the Ear The acoustic impedance at the tympanic membrane was measured at frequencies in the range 100–1000 Hz and found to be abnormal on the affected side in four patients with acoustic neuroma. In all four the resistance was abnormally high at low frequencies on the affected side, and in three the ... Forum
Forum  |   August 01, 1973
Acoustic Neuromas and the Acoustic Impedance of the Ear
 
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Forum   |   August 01, 1973
Acoustic Neuromas and the Acoustic Impedance of the Ear
Journal of Speech and Hearing Disorders, August 1973, Vol. 38, 345-353. doi:10.1044/jshd.3803.345
History: Received March 20, 1973 , Accepted April 13, 1973
 
Journal of Speech and Hearing Disorders, August 1973, Vol. 38, 345-353. doi:10.1044/jshd.3803.345
History: Received March 20, 1973; Accepted April 13, 1973

The acoustic impedance at the tympanic membrane was measured at frequencies in the range 100–1000 Hz and found to be abnormal on the affected side in four patients with acoustic neuroma. In all four the resistance was abnormally high at low frequencies on the affected side, and in three the reactance of the affected ear was raised relative to that of the contralateral ear, particularly at low frequencies. The abnormality is attributed to an increase in the input acoustic impedance of the cochlea produced by the increase in protein content of the cochlear fluids and dilatation of the cochlear duct known to occur in acoustic neuroma. This explanation is supported by theoretical calculations carried out on an electric analogue of the conductive system, and it is suggested that similar abnormalities in the acoustic impedance at the tympanic membrane might occur in other pathologies which produce abnormal mechanical conditions in the cochlea.

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