Sound pressure distribution and power flow within the gerbil ear canal from 100Hzto80kHz

Abstract

Sound pressure was mapped in the bony ear canal of gerbils during closed-field sound stimulation at frequencies from 0.1 to 80 kHz. A 1.27-mm-diam probe-tube microphone or a 0.17-mm-diam fiber-optic miniature microphone was positioned along approximately longitudinal trajectories within the 2.3-mm-diam ear canal. Substantial spatial variations in sound pressure, sharp minima in magnitude, and half-cycle phase changes occurred at frequencies >30 kHz. The sound frequencies of these transitions increased with decreasing distance from the tympanic membrane (TM). Sound pressure measured orthogonally across the surface of the TM showed only small variations at frequencies below 60 kHz. Hence, the ear canal sound field can be described fairly well as a onedimensional standing wave pattern. Ear-canal power reflectance estimated from longitudinal spatial variations was roughly constant at 0.2-0.5 at frequencies between 30 and 45 kHz. In contrast, reflectance increased at higher frequencies to at least 0.8 above 60 kHz. Sound pressure was also mapped in a microphone-terminated uniform tube-an "artificial ear." Comparison with ear canal sound fields suggests that an artificial ear or "artificial cavity calibration" technique may underestimate the in situ sound pressure by 5-15 dB between 40 and 60 kHz.

Gerbil middle-ear sound transmission from 100Hzto60kHz

“…13 that reactance and reflectance increase above the maximum frequency where a cochlear traveling wave can form and ͑b͒ the increase in EC sound power reflectance R EC above 50 kHz observed by Ravicz et al ͑2007͒.…”

“…At MEEI, P EC was measured at various locations within the bony EC remnant with a custom probe tube microphone ͑based on a Larson-Davis 2520 1/4-in. condenser microphone, Provo, UT-see Ravicz et al, 2007;1.27 mm outer diameter͒ that was advanced ϳ0.5-1 mm down the bony EC toward the TM along an approximately longitudinal trajectory ͓see Ravicz et al, 2007, Fig. 2͑b͔͒.…”

“…The system used at MEEI is described in Ravicz et al ͑2007͒. Stimuli were broadband chirps 0.05-99 kHz, and vibrometer and microphone responses were digitized at 225 kHz.…”

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.…”

A study of sound transmission in an abstract middle ear using physical and finite element models

“…A finite element model (FEM) of the system was developed, and its predictions were used to interpret the experimental results. Many previous studies have employed pressure measurements within the EC and acoustic models with various objectives: for example, to quantify ME transmission, to understand transmission of otoacoustic emissions, and to diagnose middle ear pathology (e.g., Keefe et al, 1993;Ravicz et al, 2007;Puria and Allen, 1998;Stinson, 1985). The present model is more abstract than these, and its strength lies in the precise matching between experimental and modeling results.…”