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

The exterior effects room (EER), located at the NASA Langley Research Center, was recently upgraded to allow for simulation of aircraft flyovers in a three-dimensional (3-D) audio and visual environment. The 3-D audio server employs an implementation of the vector base amplitude panning (VBAP) method to position virtual sources at arbitrary azimuth and elevation angles in the EER. Recent work focused on the development of loudspeaker equalization first using high order FIR filters [POMA 9 015004 (2010)], and later using low order IIR filters [J. Acoust. Soc. Am. 128 2482 (2010)]. The latter, in conjunction with full-path time delay compensation and relative gain compensation, were implemented in real-time and shown to reproduce the desired sound field to within about ±5 dB over an extended frequency range for stationary and moving sources. In the present work, the performance is further characterized both objectively and subjectively. Addressed are calibration of the system for absolute sound pressure level reproduction and measurement of the spatial uniformity of the generated sound field. Further, localization of sound sources will be subjectively measured to assess the efficacy of the VBAP implementation in the EER.