Acoustic performance of an installed real-time three-dimensional audio system

The Exterior Effects Room (EER), located at the NASA Langley Research Center, is a facility built for psychoacoustic studies of aircraft community noise. Recently, the EER was significantly upgraded to allow for simulation of aircraft flyovers in a 3-D audio and visual environment. The upgrade included installation of 27 satellite and 4 subwoofer loudspeakers that are driven by a real-time audio server. The audio server employs an implementation of the vector base amplitude panning method to position virtual sources at arbitrary azimuth and elevation angles in the EER. Real-time application of filters, time delays, and gains are required to compensate for installation effects, including those associated with the irregular room geometry, colorization due to varying loudspeaker installations, and crossover filtering. The authors previously showed [J. Acoust. Soc. Am., 127, 1969 (2010)] that color compensation and crossover filtering could be achieved for satellite and subwoofer loudspeakers. However, the resulting FIR filters were too long (32 768 taps) to implement in real-time. The focus of this work is on the development of reduced-length surrogate IIR filters and on the measurement of the acoustic performance of the installed real-time system.