Spatial aspects of sound quality - and by multichannel systems subjective assessment of sound reproduced by stereo

The reproduction of sound by stereo and by multichannel systems is affected by many factors which will give rise to various complex sensations in listeners, and thereby influence the perceived overall quality. In this Ph.D. thesis, the perceptual changes associated with different reproduction scenarios are assessed experimentally, with an emphasis on spatial aspects. In stereophony, virtual sound sources are created between the loudspeakers by feeding them with coherent signals, differing in intensity (intensity or amplitude panning) or delayed in time (delay panning). In order to assess the fidelity with which sound reproduction systems can re-create the desired stereo image, a laser pointing technique was developed to accurately collect subjects' responses in a localization task. This method is subsequently applied in an investigation of the effects of loudspeaker directivity on the perceived direction of panned sources. The second part of the thesis addresses the identification of auditory attributes which play a role in the perception of sound reproduced by multichannel systems. Short musical excerpts were presented in mono, stereo and several multichannel formats to evoke various spatial sensations. Eight of these attributes (width, brightness, spaciousness, elevation, distance, envelopment, naturalness and clarity) were identified and quantified in a series of experiments. Finally, the relation between these specific attributes and overall preference was formulated in a statistical model.