Abstract: A filter and method of adapting a digital filter provides a single fixed finite impulse response (FIR) filter adaptively from measured data, in a manner whereby the filter's frequency and time resolution can be controlled. The resulting filter exhibits properties which allow it to be efficiently implemented in various multi-rate configurations. Specifically, the system and method produce an FIR filter with high resolution at low frequencies by having a large number of coefficients, but reduces resolution at higher frequencies by allowing only a fraction of the coefficients to adapt to the high frequency part of the signal. This is accomplished by using a multi-rate, segmented adaptation procedure, such that resolution and bandwidth are controlled independently at each state. If desired, the resulting filter can be made to approximate constant Q resolution. In addition, by adapting only a short part of the filter at a time, misadjustment is minimized.