An audio processing device is disclosed. The audio processing device includes a filter and an output circuit. The filter is configured to receive an audio signal to generate a filtered audio signal, wherein the filter includes a plurality of parameters that are adjustable for changing a bandwidth, a center frequency or a gain of response of the filter. The output circuit is configured to receive the filtered audio signal to generate an output audio signal to a speaker. When the parameters of the filter are changed, the filter reduces changes in the audio signal caused by the parameters, and the output circuit continuously receives the filtered audio signal to generate the output audio signal for the speaker to play without interruption.