ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

4aMU3. The guitar: Air modes and radiated sound fields.

Ingolf Bork

Ulrich Heise

Physikalisch-Technische Bundesanstalt, Braunschweig, Germany

Uwe J. Hansen

Indiana State Univ., Terre Haute, IN 47809

The experimental technique of modal analysis is generally used to display normal modes of structural vibrations. It provides a phase sensitive method of representing a slow motion animated display of the standing waves supported by the structure. The technique also allows exaggerated displacement representation on the computer screen for ease of observation. An essential element in the technique is associated with its ability to retain spatial phase information for a predetermined geometrical point distribution on the structure in relation to the point of excitation. The work discussed in this paper utilizes this ability to retain phase information and extends the technique to represent the radiated sound field. The grid of observation points is removed from the structure and is replaced by a grid covering the space where the sound field is to be modeled. The excitation point is retained on the structure. This will be illustrated by observing air resonances in a guitar in computer animation, and by representing the radiated sound field of that guitar at various frequencies.