Subband signal processing is an important tool in numerous applications such as acoustic echo cancellation, noise reduction, signal enhancement, adaptive beam forming, and signal separation, among other applications. Subband signal processing uses a filter bank to split each input signal into a set of frequency signals, each covering a fraction of the input signal bandwidth. Subband processing provides an efficient way to divide and conquer tedious problems by a set of parallel and smaller subband algorithms. In many cases, the subband processing is performed together with decimation, which reduces the dimensionality of the data in the subband algorithm. The focus in this article is on temporal subband processing, i.e., time-frequency transformation, although spatial subband processing may also gain from the discussion here.