Audible reflection density for different late reflection criteria in rooms

摘要

For reasonably accurate but practical auralizations, some simplifications andapproximations are needed. The main issue in the present investigation is that thereflection density of a room impulse response, in theory, increases so fast as a quadraticfunction of the elapsed time, even assuming only specular reflections. Therefore in thisstudy, the upper threshold for audible reflection density is investigated for four differenttransition times of 25, 50, 75, and 100 ms through a headphone listening test. Binauralimpulse responses and speech signals simulated in three rooms with differentcharacteristics (an empty office, a lecture room, and an auditorium) are used as stimuli.Subjects are asked to increase/decrease the reflection density of a stimulus until theycannot distinguish it from the stimulus that follows the theoretical reflection density for thedifferent transition times in the three rooms. When using binaural impulse responses, theupper limit of the audible reflection density turns out to be limited to 2800 reflections persecond. For speech signals, the maximum audible reflection density is shown to be as low as300 reflections per second, regardless of the room and transition time.