Measurement of the acoustic input immittance of the human ear

Abstract

A method is presented for measuring acoustic immittance (admittance or impedance) in the human ear canal and its validity is demonstrated for frequencies from 62 Hz to 4 kHz. Special attention is given to estimating the residual ear-canal space between the eardrum and the tip of the measuring device; estimates were determined, in part, using immittances measured with static pressures applied in the ear canal. Immittance estimates at the eardrum are reported for four normal subjects. Below 500 Hz, the immittance is compliance dominated. Our averaged compliance equivalent to 0.70 cc agrees with that reported by others. From 1 to 4 kHz, the immittance is resistance dominated. Our resistance values exceed those generally reported previously; they are, however, similar to those of Mehrgardt and Mellert [J. Acoust. Soc. Am. 61, 1567--1576 (1977)] and to values suggested from analysis of other acoustical measurements on the external ear.

An Analysis of the Acoustic Input Impedance of the Ear

“…The frequency response of the normalized input admittance of the middle ear is bandpass, similar to that reported by Rabinowitz (1981) up to 4 kHz, with the middle ear becoming mass-controlled above 4 kHz. The frequency response differs from the more narrowly tuned response reported by O'Connor and Puria (2008), suggesting that postmortem changes may simplify the tuning properties of the middle ear although Voss et al (2000) reported an input impedance magnitude and phase from temporal bones more consistent with Figure 4.…”

“…Previous studies of the acoustic input impedance of the ear include lumped element models of the human middle ear (e.g., Kringlebotn 1988;Moller 1961;Zwislocki 1962), experimental studies of the middle ear of human temporal bones (e.g., O'Connor and Puria 2008;Voss et al 2000), experimental studies of human ears (e.g., Farmer-Fedor and Rabbitt 2002;Kringlebotn 1994;Margolis et al 1999;Moller 1965;Rabinowitz 1981;Voss and Allen 1994), and models and experimental studies of animal ears (e.g., Huang et al 2000;Lynch et al 1994;Parent and Allen 2007). Prior to 1981, experimental studies of the acoustic input impedance of the ear in humans were limited to about 1.5 kHz, the ear canal treated as an acoustic compliance (Rabinowitz 1981).…”

“…Prior to 1981, experimental studies of the acoustic input impedance of the ear in humans were limited to about 1.5 kHz, the ear canal treated as an acoustic compliance (Rabinowitz 1981). The ear canal, modeled as a one-dimensional transmission line, extends the upper frequency limit to where sound deviates from propagating predominantly as plane waves.…”

Structures that contribute to middle-ear admittance in chinchilla

“…This difference in hole size accounts for the difference in the frequency of the air-space and hole anti-resonance. (Zwislocki 1962& Rabinowitz 1981 and in the ears of two patients with missing inci (Zwislocki 1962). (C) and (D) Comparisons of admittance measured in individual rabbit and cat ears made with the middle-ear air spaces widely opened, before and after interrupting the ossicular chain (Møller 1965).…”

“…Knowledge of these source parameters permitted us to calculate the acoustic admittance at the measurement site within the ear canal coupler Y EC . The admittance at the tympanic membrane Y TM was calculated from the ear-canal admittance using a transmission-line correction based on the dimensions of the ear coupler and post-experiment fluid-filling measurements of the residual ear-canal volume between the coupler and the TM (Møller 1965;Rabinowitz 1981;Lynch et al 1994). The units of acoustic admittance are siemens (S), where 1 S equals 1 Pa-s-m −3 .…”