Non-invasive estimation of middle-ear input impedance and efficiency

Area of Science:

• Audiology
• Acoustics
• Biomedical Engineering

Background:

• Wideband acoustic immittance measurements are crucial for assessing middle ear function.
• Ear canal impedance (ZEC) measurements are sensitive to probe placement, potentially affecting accuracy.
• Transforming ZEC to eardrum impedance (ZED) aims to mitigate probe-placement variability.

Purpose of the Study:

• To describe and validate a method for transforming ZEC to ZED.
• To assess the impact of this transformation on probe-depth sensitivity.
• To evaluate the estimation of middle ear (ME) efficiency using ZED.

Main Methods:

• Modeled the ear canal as conical segments.
• Incorporated a middle ear and cochlea model.
• Performed acoustic measurements of ZEC at two probe locations in 15 subjects.

Main Results:

• ZEC measurements showed significant sensitivity to probe location, especially near resonance frequencies.
• Transforming ZEC to ZED reduced insertion-depth sensitivity between 1 and 12 kHz.
• Absorbance (A) showed intermediate probe-placement sensitivity compared to ZEC and ZED.

Conclusions:

• The ZEC to ZED transformation effectively reduces probe-placement sensitivity, particularly at higher frequencies.
• Estimated middle ear efficiency exhibited a bandpass characteristic, peaking between 1-4 kHz.
• ZED and ME efficiency estimates hold potential for advancing wideband acoustic immittance diagnostics.