| Page 82
30.09.2007 Angelo Farina
UNIPR | All Rights Reserved | Confidential
High-frequency
cancellation due to averaging
§When
several impulse response measurements are synchronously-averaged for improving the S/N ratio, the late part of the tail
cancels out, particularly at high
frequency, due to slight time variance of the system
Comparison of a single
sweep 50 s long with the synchronous average of 50 sweeps, 1 s long each.
Spectrum of a single sweep of 50s (above)
versus 50 sweeps of 1s (below)
short-FFT spectrum at 200 ms after direct sound
short-FFT spectrum at 200 ms after direct sound
4 kHz
4 kHz