From WD6CNF:

DSP Audio Filter is a program designed to enable you to filter the audio input (microphone) with one of several filters and then output it to the computer speakers. It has different audio digital filters include two band pass filters, three notch filters, and two noise filters. It provides graphical setting of filter center frequency and bandwidth, microphone input and speaker output, file record and playback filtered audio, and frequency or time display.
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