Acoustic calibration of the exterior effects room at the NASA Langley Research Center.

Abstract

The exterior effects room (EER) at the NASA Langley Research Center is a 39-seat auditorium built for psychoacoustic studies of aircraft community noise. The original reproduction system employed monaural playback and hence lacked sound localization capability. In an effort to more closely recreate field test conditions, a significant upgrade was undertaken to allow simulation of a three-dimensional (3-D) audio and visual environment. The 3-D audio system consists of 27 full-range satellite speakers and four subwoofers, driven by a real-time audio server running a derivation of vector base amplitude panning. The audio server is part of a larger simulation system, which controls the audio and visual presentation of recorded and synthesized aircraft flyovers. The focus of this work is on the calibration of the 3-D audio system, including gains used in the amplitude panning algorithm, speaker equalization, and absolute gain control. Because the speakers are installed in an irregularly shaped room, the speaker equalization includes time delay and gain compensation due to different mounting distances from the focal point, filtering for color compensation due to different installations (half space, corner, and baffled/unbaffled), and crossover filtering.