A possibility of sharp tuning in a linear transversally inhomogeneous cochlear model

Area of Science:

• Auditory Neuroscience
• Biophysics
• Acoustics

Background:

• The basilar membrane's frequency selectivity is crucial for hearing.
• Previous cochlear models often simplified its complex geometry.
• Understanding the role of transverse geometry is key to explaining auditory tuning.

Purpose of the Study:

• To investigate the impact of cochlear transverse geometry on basilar membrane mechanics.
• To develop a linear hydromechanical model that incorporates cross-sectional details.
• To assess if this model can replicate experimental findings on frequency selectivity and phase lag.

Main Methods:

• Developed a three-dimensional linear hydromechanical cochlear model.
• Utilized WKB-approximation for calculations.
• Employed the classical Ritz's method to determine basilar membrane cross-sectional eigenfunctions.
• Calculated transversally averaged mass density and stiffness.

Main Results:

• The model demonstrated significant sharpening of frequency selectivity and decreased phase lag when transverse geometry was included.
• Tuning qualities (Q10) and phase angles at characteristic frequency (CF) fell within experimentally observed ranges.
• Cochlear cross-section size and shape were found to influence tuning.
• Damping remained negligible until the peak response, where wave-number imaginary part increased sharply.

Conclusions:

• Transverse geometry is a critical factor in achieving realistic basilar membrane frequency selectivity and phase response.
• The developed model, incorporating cross-sectional details, successfully reproduces key experimental auditory data.
• This approach provides a more accurate framework for understanding cochlear mechanics and auditory processing.