Prediction of random errors in sound intensity measurement

It is well known that the random errors of sound intensity estimates can be much larger than the theoretical minimum value determined by the BT-product, in particular under reverberant conditions, in the near field of structural sources, and when there are several independent sources present. More than ten years ago it was shown that one can predict the random errors of estimates of the sound intensity in, say, one-third octave bands from the power and cross power spectra of the two signals from a sound intensity probe, determined with fine spectral resolution with a dual channel FFT analyser. That is not very practical, though. This work demonstrated that one can predict the random errors from the power and cross power spectra determined with the same spectral resolution as the sound intensity itself.