Abstract:

NASA is conducting a research program in passenger response to aircraft interior noise to develop tools for use in design decisions for interior noise treatments. A new interior simulator has been built at NASA--Langley to be used in this program. The simulator is a shell fitted with interior trim and seats from 737/727 aircraft. It contains five listening stations, each having a pair of headphones for binaural signal presentation. Binaural recordings made in interiors of a number of aircraft were processed on a workstation into 50 sound stimuli. These were played back over the headphones and analyzed for repeatability within and between headphones. Initial results indicated that ranges averaged within headphones were 0.3 dB (A weighted), 0.3 phons and 0.7 dB (unweighted). When averaged between headphones, ranges were 1.0 dB (A weighted), 0.9 phons and 1.4 dB (unweighted). A first test in the simulator presented stimuli from propeller airplanes digitally modified to reduce the tonal components. Regressions between subjects' preference responses and measured metrics indicate that the subjective response correlates as well with the arithmetic mean of measurements from the left and right ears of the headphones as with the energy or pressure sums, and better than with measurements from the worse ear.