## Monday, February 27, 2006

### all-pass filter

All-pass filter

The allpass filter is an important building block for digital audio signal processing systems. It is called allpass'' because all frequencies are passed'' in the same sense as in lowpass'',
highpass'', and bandpass'' filters. In other words, the amplitude response of an allpass filter is 1 at each frequency, while the phase response (which determines the delay versus frequency) can be arbitrary. So the phases are changed with various frequencies

In practice, a filter is often said to be allpass if the amplitude response is any nonzero constant.