A filter bank is a collection of band-pass filters that separates the input signal into several components, each one carrying a single frequency sub-band of the original signal. It also is desirable to design the filter bank in such a way that subbands can be recombined to recover original signal. The first process is called analysis, while the second is called synthesis. The output of analysis is referred as subband signal with as many subbands as there are filters in filter bank. The filter bank serves to isolate different frequency components in a signal. This is useful because for most applications some frequencies are more important than others.