Chinchilla middle-ear admittance and sound power: High-frequency estimates and effects of inner-ear modifications

Abstract

The middle-ear input admittance relates sound power into the middle ear (ME) and sound pressure at the tympanic membrane (TM). ME input admittance was measured in the chinchilla ear canal as part of a larger study of sound power transmission through the ME into the inner ear. The middle ear was open, and the inner ear was intact or modified with small sensors inserted into the vestibule near the cochlear base. A simple model of the chinchilla ear canal, based on ear canal sound pressure measurements at two points along the canal and an assumption of plane-wave propagation, enables reliable estimates of Y(TM,) the ME input admittance at the TM, from the admittance measured relatively far from the TM. Y(TM) appears valid at frequencies as high as 17 kHz, a much higher frequency than previously reported. The real part of Y(TM) decreases with frequency above 2 kHz. Effects of the inner-ear sensors (necessary for inner ear power computation) were small and generally limited to frequencies below 3 kHz. Computed power reflectance was ~0.1 below 3.5 kHz, lower than with an intact ME below 2.5 kHz, and nearly 1 above 16 kHz.

Stapes Vibration in the Chinchilla Middle Ear: Relation to Behavioral and Auditory-Nerve Thresholds

“…4A of (Ravicz and Rosowski 2013b)) actually have bandwidths not too dissimilar from that of the present stapes-velocity curve. It is only after corrections (to compensate for the apparent existence of standing waves) were applied that the bandwidths became sharply restricted, possibly reflecting an overcorrection based on an ear-canal model (Ravicz and Rosowski 2012) The Bandwidths of Stapes-Velocity Magnitudes, Auditory-Nerve Thresholds, and Behavioral Thresholds Figure 7 compares stapes-vibration sensitivity (Figs. 3 and 4) with the sensitivity of high spontaneous rate chinchilla auditory-nerve fibers (brown trace), computed from characteristic frequency average-rate thresholds (Temchin et al 2008b).…”

Inner-ear sound pressures near the base of the cochlea in chinchilla: Further investigation

“…This paper is a continuation of our examination of sound power transmission through the external and middle ear (ME) to the cochlear partition (CP) (Ravicz and Rosowski, 2012b). In this paper we examine the ME pressure gain, defined as the transformation of ear canal (EC) sound pressure to sound pressure inside the oval window (OW), and the sound pressure difference across the CP near the base of the cochlea in chinchilla.…”

“…In this paper we present G MEP and DP CP computed from measurements of P V , P ST , and sound pressure in the EC P near-TM in seven individual chinchillas. [ME input admittance (Ravicz and Rosowski, 2012b) and stapes velocity (Ravicz et al, 2011) were also measured in these same animals.] We also examine the effect of simple preparationrelated ME and cochlear manipulations on P V , P ST , and DP CP .…”

Sound pressure distribution within natural and artificial human ear canals: Forward stimulation

“…At each measurement location, a broadband spectrum was recorded, P EC was computed by normalizing by P TM at the umbo, and the nodal frequencies at each location were identified as the frequencies of jP EC j notches (per Ravicz et al, 2007Ravicz et al, , 2012 or the frequencies at which the unwrapped /P EC is an odd multiple of 1/4 cycle (the midpoints of 0.5-cycle /P EC steps, per Stinson, 1985a;Chan and Geisler, 1990). Data at the identified nodal frequencies were collected from all measurement locations and arranged into longitudinal maps.…”