研究目的
Investigating the inversion method for jointly estimating ear-canal cross-sectional area function and eardrum reflectance, given the acoustic reflectance measured at the entrance of the ear canal.
研究成果
The relationship between the spatial bandwidth of the estimated area functions and the frequency bandwidth of the reflectance used in the inversion is discovered for the first time. Accurate estimates of ear-canal area functions require the measurement bandwidth Fc of ear-canal reflectance to be high enough so that 2Fc/c>Bspatial, where Bspatial is the actual spatial bandwidth of ear-canal area functions under test.
研究不足
The spatial bandwidth of the estimated area functions is determined by the frequency bandwidth of the reflectance used in the inversion. If the actual spatial bandwidth of the area function under estimation is higher than this, Gibbs ripples appear in the estimated area function.
1：Experimental Design and Method Selection:
The study uses an acoustic impedance tube with inner diameter 8 mm to measure ear-canal reflectance, avoiding non-planar waves. The excitation signal is an exponential chirp from 20 Hz to 20 kHz. Sound response signals at five positions in the tube are used to measure the ear-canal reflectance.
2：Sample Selection and Data Sources:
Measurements were performed on one male and one female subject in a sound-proof booth.
3：List of Experimental Equipment and Materials:
Acoustic impedance tube, insert earphone, miniature microphone (diameter 2.5 mm).
4：5 mm).
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The impedance tube was tightly connected to the ear canal. The excitation signal was played five times, and each time the same miniature microphone was inserted in the tube to record the sound signal at one of the five positions.
5：Data Analysis Methods:
The frequency responses of the incident and reflected sound pressure signals were obtained, and the sound pressure reflection coefficient at the reference plane was calculated.
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