A hot topic in musical acoustics: Phase coherent representation of radiated sound fields.

Abstract

A technique used to study normal‐mode vibrations in musical instruments is modal analysis. This experimental method analyzes a series of transfer functions which relate the frequency spectra of a number of impact points to the spectrum of a fixed response point, and subsequently presents the motion of the structure at the various normal‐mode frequencies in computer animation. This approach is extended to represent a radiated sound field by using a fixed excitation point on the musical instrument as the reference signal and monitoring the sound field with a microphone at a number of predetermined points. This makes it possible to relate the phase of the sound field to the phase of the vibrating structure responsible for generating that field. Animated illustrations will be shown for the air column in a wind instrument and for the sound field of a concert grand piano.