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Table 1
Coordinate Determinants
Speaker Default Alternative
Coordinate Distances Distances
Y1 D2-DI D3-D4
Xl D4-D1 D3-D2
Y2 D7-D8 D6-D5
X2 D8-D5 D7-D6
A raw position datum for a sp-mic pair is a 16 bit
integer corresponding to the number of (approximately) 1 Mhz clock cycles that occurred between the beginning of the acoustic source driver pulse and the detection of the third peak of the microphone/detector's ringing response (see section 2.1.1). The expression of the relationship between this number and the distance from the acoustic source to the microphone detector is
(4) C = mD + b
where C is the number of clock cycles, D is the distance, m is a factor related to the speed of sound in air, and b is a constant resulting from the delays involved with the transmission and the detection of the sound front. It was empirically determined that for all the sp-mic pairs
m = 28.46 cycles/mm with a variance of 0.0006
and b = 175.5 cycles with a variance of 31.0
which is reasonable since m is a physical constant and b is a function of variability in electronic components.
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