Accession Number : AD0732041

Title :   Some Acoustic Phenomena Related to Curved Surfaces,

Corporate Author : CALIFORNIA UNIV LOS ANGELES SCHOOL OF ENGINEERING AND APPLIED SCIENCE

Personal Author(s) : Hamet,Jean-Francois

Report Date : SEP 1971

Pagination or Media Count : 90

Abstract : In the first part of the dissertation, the successive reflections of a spherical front inside a circular cylindrical enclosure are considered. The spherical front is centered on the axis of the cylinder. The reflecting surface is assumed to be perfectly rigid. A geometrical acoustics study of the reflected field is given, together with its limitations. Using an integral representation of the solution for the reflected field, it is then shown how one can obtain the geometry of the successive reflected fronts, together with the amplitude and phase of the reflected signal in the neighborhood of the fronts. The 'radial focusing effect' is studied. It is also proved that, if the reflected fronts seem to emanate from a set of ring sources, these are not images in the ordinary sense of the term. In the second part, independent from the first one, the 'whispering gallery phenomenon' is considered for the vase of a spherical enclosure. Using an asymptotic expansion method, it is shown how a whispering signal may propagate along the wall of the enclosure, either along great circles in an axisymmetric way, or along one great circle only. A comparison is made with the solution obtained by using the normal modes method. Some comments are made about the difficulty of studying the 'forced modes,' i.e., the whispering signal when a source is present. (Author)

Descriptors :   (*SOUND TRANSMISSION, CURVED PROFILES), SPHERES, PROPAGATION, FOCUSING, REFLECTION, INTEGRAL TRANSFORMS, CYLINDRICAL BODIES, THESES

Subject Categories : Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE