The AR order box determines the level of prewhitening. When AR orderequals 0, the SI Estimate Impulse Response VI does not apply prewhiteningto the system. When AR order is small and you do not place a checkmarkin the is white noise? checkbox, the variance of the impulse response islarge because the input signal is not always white noise. The greater thevalue of AR order, the better the VI whitens the signal, but the morecomputation time and memory the VI requires