ASA 125th Meeting Ottawa 1993 May

3pPP10. Use of auralization to accomplish small elevation shifts of a loudspeaker in the median plane.

David L. Bowen

RH Lyon Corp., 691 Concord Ave., Cambridge, MA 02138

Jens Blauert

Ruhr-Universitat Bochum, Bochum, Germany

The use of frequency domain equalization to change the perceived elevation of a loudspeaker over a fairly small range in the frontal plane ((plus or minus)20(degrees)) will be described. Because of the application (the center channel speaker in home video theater), several constraints were in effect. Among these were (1) the effect must be applicable over a broad range of people, and over a fairly broad listening area, (2) the equalization applied must not introduce an objectionable amount of ``coloration'' into the sound, and (3) the resulting circuit must be feasible to implement into a consumer product. The procedure used was to first determine equalizations from ratios of head-related transfer functions measured on an artificial head and on human subjects. Salient features were then determined and implemented in hardware for listening tests, where further refinements took place. Despite a common assertion that there is little directional dependence in the median plane below 4--5 kHz, listening tests indicated a more convincing effect took place when several features below 4 kHz were included in the equalizations. It was also found effective to include a feature at 12.5 kHz, even if source material was limited to male speech. The results of demonstrating a 20(degrees) to 0(degrees) ``delevator'' to 125 groups of 12 people will also be discussed. [Work supported by Thomson Consumer Electronics.]