Specification of the geometry of the human ear canal for the prediction of sound-pressure level distribution

Abstract

The geometry of 15 human ear canals has been studied. Silicone rubber molds were made of the ear canals of human cadavers, and a mechanical probe system was used to obtain approximately 1000 coordinate points over the surface of each mold. The data points were accurate to about 0.03 mm in each of the three space directions, allowing ample resolution of surface detail. The measurements have been summarized as individual ear canal area functions, the area of cross-sectional slices normal to a curved central axis following the bends of the canal. Large intersubject differences were found, but several overall trends were evident in the area functions. Accurate specification of the canal geometry has lead to improved predictions of the sound-pressure distribution along the human ear canal at frequencies greater than 8 kHz. Such predictions are relevant to the development of high-frequency audiometric methods, high-fidelity hearing aids, and to the interpretation of experiments in physiological and psychological acoustics.

Building and Testing a Statistical Shape Model of the Human Ear Canal

“…Measurements of the anatomy of a single ear canal have been made for the purpose of prediction of sound-pressure level distribution [1]. Manufacturers of hearing aids have made initial testing of rapid prototyping of hearing aid shells using laser scans of ear impressions but have not performed statistical analysis of these.…”

Basal Contributions to Short-Latency Transient-Evoked Otoacoustic Emission Components

“…The inner diameter of the tube was selected to approximate that of the average adult ear canal (Stinson and Lawton 1989). The long-tube calibration was used as the pressure measured by the probe microphone at the entrance to the tube in insensitive to standing-wave effects which can otherwise introduce errors during in-situ SPL ear-canal calibrations (Sachs and Burkhard 1972;Stinson et al 1982;Gilman and Dirks 1986).…”

Numerical Analysis of the Influence of the Auditory External Canal Geometry on the Human Hearing Response

“…Different numerical models have been developed. In order to have a comparison pattern of the results of this study, a EAC basic model was built based on real measurements taken from literature [7]. Using CAD tools, cross sections were obtained and placed perpendicular to the curved axis passing through the centroid of each section.…”

“…All dimensions were taken according to experimental measurements made by [7] and [8]. This model is design to enable the change of the tympanic membrane orientation with respect to the lateral wall (angle θ ) and top wall (angle Φ) of canal, as well as in order to model the decrease of the isthmus section.…”

“…The relative position and orientation of the tympanic membrane and section reduction of the canal at the isthmus were studied with a harmonic analysis. (a) Geometry of tympanic ossicular system with the EAC model based on measurements made by [7]. (b) EAC model with elliptical cross section and straight axis.…”