An investigation of listener envelopment utilizing a spherical microphone array and third-order ambisonics reproduction

Listener envelopment (LEV), the sense of being surrounded by the sound field, is a perception that has been found to be related to the overall impression of a concert hall. The purpose of this study was to investigate the relationship between the perception of LEV and the direction and arrival time of energy from spatial room impulse responses (IRs). IRs were obtained in a 2000-seat concert hall using a 32-channel spherical microphone array and analyzed using a third-order plane wave decomposition. Additionally, the IRs were convolved with anechoic music and processed for third-order Ambisonic reproductions and presented to subjects over a 30-loudspeaker array. Instances were found in which the energy in the late sound field did not correlate with LEV ratings as well as energy in a 70-100 ms time window. Follow-up listening tests were conducted with hybrid IRs containing portions of an enveloping IR and an unenveloping IR with crossover times ranging from 40 to 140 ms. Additional hybrid IRs were studied wherein portions of the spatial IRs were collapsed into all frontal energy with crossover times ranging from 40 to 120 ms. The tests confirmed that much of the important LEV information exists in the early portion of these IRs.