Effects of interchannel crosstalk in multichannel microphone technique
Even though the significance of interchannel crosstalk in multichannel microphone technique has been an issue of much debate in the field of sound recording, any effects on the perception of reproduced phantom images have not been investigated systematically. There is consequently no experimental data to which sound engineers can refer when attempting to control interchannel crosstalk in the design and application of multichannel microphone technique. It was therefore necessary to investigate the effects of such interchannel crosstalk in both the perceptual and the physical domains.
Extant multichannel microphone techniques were reviewed, concentrating on their crosstalk characteristics. Findings from concert hall and room acoustics studies relating to the effects of early reflections, which might be the basis for understanding the perceptual effects of interchannel crosstalk, were also studied.
The effects of interchannel time and intensity relationship and sound source type on the perception of stereophonic phantom image attributes were first examined in the context of two-channel stereophonic reproduction. The perceptual attributes of phantom sources affected by interchannel crosstalk in three- channel microphone technique were then elicited, and the effects of interchannel time and intensity relationship, sound source type and acoustic condition on the perception of those attributes were investigated. The effects of interchannel crosstalk on sound quality preference were also examined in both controlled and practical manners. Finally, following objective measurements of experimental stimuli, relationships were established between the perceptual and objectively measured effects of interchannel crosstalk.
It was found that the most salient perceptual effects of interchannel crosstalk were an increase in source width and a decrease in locatedness. The relationship between interchannel time and intensity differences involved in the crosstalk signal was significant for both effects. The type of sound source was significant only for the source width effect whereas the acoustic condition was significant only for the locatedness effect. The source width increase was mainly influenced by the middle frequencies of crosstalk signals in a region of the spectrum around 1000Hz, at the onsets of the signal envelopes. The results of listener preference experiments suggested that the preference for interchannel crosstalk would depend on the spectral and temporal characteristics of sound source to be recorded rather than on the magnitude of interchannel crosstalk.