The eigenspectra of Indian musical drums

TL;DR

This paper models Indian musical drums with non-uniform density membranes, revealing harmonic low eigenmodes, and uses spectral methods to match experimental spectra, aiding sound synthesis.

Contribution

It introduces a non-uniform membrane model for Indian drums and applies a spectral collocation method to accurately compute eigenmodes, aligning with experimental data.

Findings

Eigenmodes of non-uniform membranes are harmonic unlike uniform ones.

Numerical eigenvalues match experimental spectra with optimized parameters.

Spectral methods effectively model complex drum head vibrations.

Abstract

In a family of drums used in the Indian subcontinent, the circular drum head is made of material of non-uniform density. Remarkably, and in contrast to a circular membrane of uniform density, the low eigenmodes of the non-uniform membrane are harmonic. In this work we model the drum head by a non-uniform membrane whose density varies smoothly between two prescribed values. Using a Fourier-Chebyshev spectral collocation method we obtain the eigenmodes and eigenvalues of the drum head. For a suitable choice of parameters, which we find by optimising a cost function, the eigenspectra obtained from our model are in excellent agreement with experimental values. Our model and the numerical method should find application in numerical sound synthesis.