On the Analytic Origin of Two Species of Cochlear Eigenmodes

TL;DR

This paper develops an analytic framework to explain the emergence of localized and extended eigenmodes in cochlear wave propagation, clarifying the structure of cochlear wave equations and advancing understanding of cochlear mechanics.

Contribution

It provides the first analytic explanation for the origin of two cochlear eigenmode types, linking them to standing waves and internal resonance phenomena.

Findings

Extended modes are from globally continuous standing waves.

Localized modes result from internal resonance at a singular point.

Clarifies the generic structure of cochlear wave equations.

Abstract

After entering the ear, sound waves propagate as surface waves along the cochlea's basilar membrane. In recent work, we showed numerically that the system supports two types of modes: localized resonant modes, which underpin the modern understanding of cochlear mechanics, and a novel class of spatially extended modes. Here, we develop an analytic framework that explains the emergence of this mode structure. We show that extended modes arise from globally continuous standing-wave solutions, whereas localized modes result from internal resonance requiring matching across a singular point. These results clarify the generic structure of cochlear wave equations.