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Proximity perception

2012-10-02 Proximity perception in concert halls:

Listen to the two 10 second violin pieces by single-click on S1 and S3 (binaural wav) below. Questions: 1) Proximity 2) Loudness 3) Reverberance. The examples are created by convolving an anechoic Mozart piece with binaural impulse responses measured with a dummy head placed in a concert hall seat, approx 8m from centre line of hall.

Results after 17 days and response count N=29 are presented below.

S1 source position at stage front; S3 source position at stage rear; Orchestra shell volume approx 1000 m3
Receiver position in S1 and S3 is exactly the same. Hall volume approx 19000 m3

Conclusions:

A minority of 14% listeners perceived the source (S1) at 15m distance (S1) to be closer than the source (S3) at 24m distance.  79% of listeners perceived S3 as closer and 7% judged the distances to be equal.

Perceived Reverberance is well predicted by EDT.
None of the distance cues suggested in litterature , e.g. sound pressure levels (G, L direct, Direct to Reverb ratio, etc) could predict the subjective outcome in this case.
Among common objective parameters only C80 and 1-IACC early coincide with perceived distance in he 29 respondents.
Mid-frequency single number averages (500-1000Hz octaves) given in table below

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More about concert hall acoustics:  http://www.akutek.info/concert_hall_acoustics.htm

More about rehearsal room acoustics: http://www.akutek.info/research_files/rehearsal_rooms.htm

Above: Cumulative IRs, normalized to G=0dB; Level interval [ -20dB, 0dB ] ; Time interval [ 0ms, 80ms ].

Comments:
Proximity judgement result is not explained by quantities suggested in litterature, but coincide with C80 and 1-IACCE
Loudness judgement is not explained by quantities suggested in litterature, but coincide with C80 and 1-IACCE
Subjective Proximity coincide with subjective Loudness, i.e. ”closer” coincide with ”louder”.
Reverberance judgement conforms with established results

Suggested explanations for misperception of distance: 1) Image sources dominates over primary source (Gearly>>L direct). As primary source move forward on stage, the ensemble of image sources in the orchestra shell moves backwards and vice versa. Thus listeners without visual cue might judge the distance to the ensemble of image sources rather than to the primary source. 2) The brain confuses Clarity with Proximity.

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