Acoustic Listening Lab
The listening lab is used to conduct human subject testing using variable acoustics. There are two rooms adjacent to each other in the acoustic listening lab – 1) the monitor chamber and 2) the listening chamber. The monitor chamber is used as a welcome area for the test participants and for conducting screening interviews. The listening chamber has a volume of approximately 900 cubic feet and sits on a floating floor structure to isolate structural vibration migrating from the nearby freight elevator. It was outfitted with drywall, with two of the walls slightly slanted to prevent flutter echoes. Bass traps are placed at three corners and additional 1-inch wall absorptive panels are attached to the back and one side wall to further reduce the reverberation time. As a result, the listening chamber has an ambient reverberation time (T20) of 0.23 seconds (averaged across 500, 1000 and 2000 Hz) and background noise level of RC-26 (hissy) – quiet and “dry” enough for us to introduce artificial signals via loudspeakers and create various virtual acoustic environments. A technique we use heavily in the listening chamber is called “auralization”, analogous to visualization but with sound. Individual listeners are immersed in the auralized environments and asked to perform certain tasks, i.e., calculation, speech comprehension, Sudoku puzzles. We can then correlate the listeners’ performance on the task with the acoustic characteristics in the auralized environments, i.e., reverberation times, background noise levels, noise impulse length and magnitude.