Abstract
In this paper we describe a system which we have developed to measure cat ear canal specific acoustic impedance Z sp , magnitude and phase, as a function of frequency, for frequencies between 200 Hz and 33 kHz, and impedance magnitudes between 4.0 to 4.0×l05 rayles (MKS). The object to be measured is placed at the end of a 3.5 mm diameter sound delivery tube. After a simple calibration procedure, which determines the Thévenin parameters for the acoustic source transducer, the impedance may be calculated from the pressure measured at the orifice of the delivery tube with the unknown load in place. This procedure allows for a fast but accurate measure of a specific acoustic impedance. The system has been tested by measuring the impedance of a long cavity and comparing this response to the exact solution of the linearized Navier Stokes equations (acoustic equations including viscosity and thermal conduction). We have used this system to measure the impedance of the normal cat tympanic membrane in more than 30 cats. Healthy animals were found to have a real input impedance of ρc between 0.3 to 20.0 kHz. When the scala vestibuli was drained, the real part of the impedance dropped to less than ρc/10 for frequencies less than 3.0 kHz. Above 3 kHz, the impedance for the drained cochlea is best described by an open circuited transmission line.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
Similar content being viewed by others
References
Beranek, L. L. (1949). Acoustic Measurements, (Wiley, New York).
Hunt, F. V. (1954). Electroacoustics, The Analysis of Transduction, and its Historical Background, Harvard Univ. Press, John Wiley and Sons, Inc., New York, pp. 187–212.
Kinsler, L. E., Frey, A. B., Coppens, A. B., and Sanders, J. V. Fundamentals of Acoustics, J. Wiley, 1982, third edition p. 206, Section 9.5.
Lynch, T. J., III (1974). “Measurements of Acoustic Input Impedance of the Cochlea in Cats,” S. M. Thesis, Massachusetts Institute of Technology, Cambridge, Ma., pp. 1–180.
Mawardi, O. K. (1949). “Measurement of acoustic impedance,” J. Acoust. Soc. Am. 21, 84–91.
Møller, A. R. (1972). The middle ear. In J.V. Tobias (Ed.), Foundations of modern auditory theory. New York: Academic Press, 1972.
Sokolich, G. W. (1977), “Improved acoustic system for auditory research,” J. Acoust. Soc. Am. Suppl. 1 61, S12.
Tonndorf, J., and Khanna, S. M. (1967). “Some properties of sound transmission in the middle and outer ears of cats,” J. Acoust. Soc.
White, R. A., Studebaker, G. A., Levitt, H., and Mook, D. (1980). “The Application of Modeling Techniques to the study of Hearing and Acoustic Systems.” In Acoustical Factors Affecting Hearing Aid Performance, G. A. Studebaker and Hockberg, Eds., Univ. Park Press, Baltimore.
Zuercher, J. C., Carlson, E. V., and Killion, M. C. (1977). “The calculation of isothermal and viscous effects in acoustical tubes,” presented at the 94th Meeting of the Acoustical Soc. Am.
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 1986 Springer-Verlag Berlin Heidelberg
About this paper
Cite this paper
Allen, J.B. (1986). Measurement of Eardrum Acoustic Impedance. In: Allen, J.B., Hall, J.L., Hubbard, A.E., Neely, S.T., Tubis, A. (eds) Peripheral Auditory Mechanisms. Lecture Notes in Biomathematics, vol 64. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-50038-1_6
Download citation
DOI: https://doi.org/10.1007/978-3-642-50038-1_6
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-540-16095-3
Online ISBN: 978-3-642-50038-1
eBook Packages: Springer Book Archive