ASA 125th Meeting Ottawa 1993 May

2pAA6. Full-wave modeling of the transmission of sound over theater seats: Near-field investigation.

Dominique J. Cheenne

Robert D. Kubik

Robert C. Maher

Ezekiel Bahar

Dept. of Elec. Eng., 209N WSEC, Univ. of Nebraska, Lincoln, NE 68588

The full-wave theory [E. Bahar, J. Acoust. Soc. Am. 89, 19--26 (1991)] is applied to a computer simulation of sound transmission across a simplified model of theater seats. The acoustic response is derived for observation points above the seats for a range of incident angles and receiver heights. The results obtained from the model study are in good agreement with the experimental data recently obtained by J. S. Bradley [J. Acoust. Soc. Am. 90, 324--333 (1991)]. The full-wave solution accounts for the acoustic pressure diffusely scattered by the chairs as well as the zero-order field scattered by the finite floor and the direct wave from the source. It suggests that the ``seat-dip effect'' is mostly due to an interference phenomenon at the observation point between the direct field and the scattered field reflected off the floor. The model allows for a detailed analysis of the effect of scattered field by the chairs, both in front of, and behind the receiver. These results suggest the need for the use of high directionality microphones that can distinguish between the forward and backward scattered acoustic pressure during future experiments.