AES Europe 2025

Immersive sound reinforcement aims to create a balanced perception of sounds arriving from different directions, establishing an impression of envelopment over the audience area. Current perceptual research shows that coverage designs featuring nearly constant decay (0dB per distance doubling) preserve the level balance among audio objects in the mix. In contrast, a -3dB decay supports a more uniform sensation of envelopment, especially for off-center listening positions. For practical reasons, point-source loudspeakers remain widely used for immersive audio playback in mid-sized venues. However, point-source loudspeakers inherently decay by -6dB per distance doubling, and using them can conflict with the design goals outlined above. In this paper, we investigate the perceived differences between point-source and line-source setups using eight surrounding loudspeakers side-by-side covering a 10m x 7m audience area. The perceptual qualities of object level balance, spatial definition, and envelopment were compared in a MUSHRA listening experiment, and acoustic measurements were carried out to capture room impulse responses and binaural room impulse responses (BRIRs) of the experimental setup. The BRIRs were used to check whether the results of the listening experiment were reproducible on headphones. Both the loudspeaker and headphone-based experiments delivered highly correlated results. Also, regression models devised based on the acoustic measurements are highly correlated to the perceptual results. The results confirm that elevated line sources, exhibiting a practically realizable decay of -2dB per distance doubling, help preserve object-level balance, increase spatial definition, and provide a uniform envelopment experience throughout the audience area compared to point-source loudspeakers.