Center for the Built Environment

This case study summarizes our efforts to optimize speech intelligibility in a medium-sized lecture hall. In addition to describing the acoustical design, we also interpret the results of our acoustical measurements. Speech intelligibility in the hall was assessed both subjectively and objectively using natural as well as amplified speech. We determined that natural speech could be clearly understood at the rear of the hall (about 50 feet from the speaker) without electronic amplification. Thus, one of our design goals was achieved. Adding sound-absorbing materials on the ceiling and selected walls reduced the reverberation time to 0.4 seconds, thereby meeting a project design goal. Due to the distributed sound absorption and low background noise level, exceptional speech intelligibility has been achieved in the room.