ASA 125th Meeting Ottawa 1993 May

1pPA14. Acoustic spiral wave field.

Peter H. Ceperley

Alon Koren

Depts. of Physics and Elec. Eng., George Mason Univ., Fairfax, VA 22030

While most low-amplitude acoustic waves in uniform media can be considered to travel straight from source to receiver, the energy flow and propagation directions in a spiral wave field change as the wave moves away from its source [P. H. Ceperley, Am. J. Phys. 60, 938--942 (1992)]. Thus, one would expect that directional microphones and acoustic imaging systems would give false information as to the location of the source in such a wave field. Two synchronized oscillators, four small speakers, and a horn were used to create a spiral wave in the laboratory. A table top robot arm and microphone were used to map out this sound field, which was then displayed in color using MathCad. The apparent propagation direction was measured using a directional microphone. [Work supported by ONR.]