Tympanic-Membrane Vibrations in Human Cadaver Ears Studied by Time-Averaged Holography

Abstract

Tympanic-membrane (TM) vibrations were studied in fresh human-cadaver specimens by means of timeaveraged holography. As with an earlier study in cats IS. M. Khanna and J. Tonndorf, J. Acoust. Soc. Amer. 51, 1904 (1972) ], the findings supported the curved-membrane hypothesis of Helmholtz. Despite a careful search for experimental artifacts, no satisfactory explanation was found to account for the fact that the present results are at variance with the stiff-plate concept of yon B(•k6sy. With respect to their quantitative evaluation, the human-cadaver data were not as clear-cut as the earlier cat data on account of anatomical differences. A number of points, which on first glance do not seem to agree with Helmholtz's concept are being discussed in the light of present or other recent findings, and explanations are being offered. These topics include: (1) the compliance of the TM; (2) the effects of differential air pressure across the TM upon middle-ear transmission; (3) the effects of TM perforations; and (4) the fact that Helmholtz's cadaver experiment, which was thought to support his hypothesis, could not be duplicated. SUBJECT CLASSIFICATION: 4.2, 4.2.1.The authors wish to dedicate this paper to the memory of Georg yon B•k•sy. labeled the "lower fold."In line with these findings, the transformer ratio of the middle ear was thought to be given by the product of the ossicular lever ratio, malleus to incus, and the area ratio, tympanic membrane to stapedial footplate. Since the lower fold contributes little if anything to the area ratio, the term "effective area" was coined. It referred to that portion of the TM which is tightly coupled to the manubrium. Its size was found to be about two-thirds of the total TM area (von B•k•sy, 1941; Wever et al. 1948). Recent findings in this laboratory (Khanna, 1970; Khanna and Tonndorf, 1972; Tonndorf and Khanna, 1970) cast doubt upon the general validity of the above concept of TM vibrations. Time-averaged holography, which allows to record the vibratory pattern of a given membrane as a whole at one instant (Powell and Stetson, 1965), showed that, at least for the case of cats, the TM is not displaced like a stiff plate. At low frequencies (f< 2000 Hz), the holographic findings were compatible with the "curved-membrane principle" of Helmholtz (1868), which the stiff-plate concept of von B•k•sy was though to have superseded. Helmholtz had argued, on the basis of the wellknown catenary principle, that the TM itself might act as a transformer. That is to say, larger displacements of lesser force in the middle of the anterior and posterior curved sections of the TM should lead to smaller displacements of larger force of the manubrium--and this was exactly what our own experiments had indicated, as least with respect to the changes in displacement.Helmholtz had attempted to verify his hypothesis by conducting a dc displacement experiment in a human cadaver specimen. His own positive results were not confirmed by Wever and Lawrence (1954), although they employed superior instrume...

Experimental and Modeling Study of Human Tympanic Membrane Motion in the Presence of Middle Ear Liquid

“…The pioneering measurement of the full-field TM motion in human temporal bones was reported by Tonndorf and Khanna (1972) using time-average holography. Recently, the full-field TM surface motion was measured using the multi-point LDV measurement (Fay et al 2005;Maftoon et al 2013), timeaverage Rosowski et al 2009) or stroboscopic holographic interferometry ; Del Socorro Hernandez-Montes et al, Cheng et al 2010Cheng et al , 2013Rosowski et al 2011), optical coherence tomography (Djalilian, et al 2008), and scanning laser Doppler vibrometry (Huber et al 2001).…”

Experimental Study of Vibrations of Gerbil Tympanic Membrane with Closed Middle Ear Cavity

“…Tonndorf and Khanna (1972) and Khanna and Tonndorf (1972) were the first to study vibration patterns of the human and cat TM by time-averaged laser holography, at frequencies up to 5 and 6 kHz, respectively. They observed that, in both species, the maximum displacement happens in the posterior region, and for frequencies beyond 2.5 kHz, the simple low-frequency vibration pattern starts to break up and vibration patterns become more complex.…”

Antropometría del Martillo en Humanos: Un Estudio Anatómico Directo

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