Filter architecture for an adaptive noise canceler in a personal audio device

A personal audio device, such as a wireless telephone, includes an adaptive noise canceling (ANC) circuit (30B) that generates an anti-noise signal from a reference microphone signal (ref) and injects the anti-noise signal into the speaker or other transducer output to cancel ambient audio sounds. A processing circuit implements one or more adaptive filters (32A, 32B, 34C, 34D) that control the generation of the anti-noise signal. At least one of the adaptive filters is partitioned into a first portion having a fixed frequency response (32A, 34C) and a second portion having a variable frequency response (32B, 34D). The first partitioned filter (32A, 32B) may be an adaptive filter that generates the anti-noise signal directly from the reference microphone signal. An error microphone (err) may be provided to measure the ambient sounds and transducer output near the transducer. The second partitioned filter is a secondary path filter (34C, 34D) which filters a desired signal that is combined with the error microphone signal to form an error signal.