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

Abstract

The use of frequency domain equalization to change the perceived elevation of a loudspeaker over a fairly small range in the frontal plane (±20°) 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° to 0° ‘‘delevator’’ to 125 groups of 12 people will also be discussed. [Work supported by Thomson Consumer Electronics.]