Auditory frequency analysis as an active dissipative process

Abstract

An active dissipative process organizes auditory frequency analysis in the mammalian cochlea. A minimal active beam model reveals that a spatially varying viscous coupling operator, $\partial_{xx}κ\partial_{xx}$, generates dissipative forces with wave--like propagation. Local energy injection and spatial redistribution compete to govern the dynamics. This balance enables the quantitative reproduction of four key features: sharp tuning, high gain, compression, and spontaneous otoacoustic emissions. Hearing thereby belongs to a broad class of nonequilibrium pattern-forming systems.

Figures (3)

• Figure 1: Physiologically grounded schematic of the model. (Left) Key anatomical and functional features of the mammalian cochlea motivating the model. (Right, top) Minimal active beam model with spatially varying viscous coupling, including a central active region ($\mu>0$) and passive absorbing boundaries. (Right, bottom) Physiological tonotopy implemented using the Greenwood frequency–position function $f(x)$Greenwood1990.
• Figure 2: (A) Sensitivity for different input levels with $\mu_0=5\times10^4$ and $\kappa_0=10^{-5}$. (B) Rate of growth (ROG). (C) Quality factor $Q_{10}$ in the $(\mu_0,\kappa_0)$ parameter space. (D) Mechanical amplification gain in the same parameter space. Black contours in (C) and (D) indicate physiologically relevant ranges.
• Figure 3: SOAEs generated by a localized reduction (notch) in the activity and viscous-coupling profiles. (A) Temporal response showing sustained spontaneous oscillations with amplitude modulation. (B) Power spectral density exhibiting a dominant emission peak accompanied by regularly spaced sidebands.