The DSP Audio Filter is a tool that enables you to filter frequencies from an audio spectrum by using your cell phone’s microphone.
This app was originally programmed for Ham Radio (Amateur Radio) operators to remove unwanted background noise and improve SSB and CW signals (Morse Code) but it can be used in different other ways.
-Bird watchers can use it to filter out higher frequencies and eliminate street noise or other disturbing low frequencies.
-Musicians can filter out a spectrum of specific instruments.
The DSP Audio filter uses a freely adjustable lowpass and highpass filter which allows you to select specific filter frequencies and bandwidths. A waterfall visually displays the incoming audio spectrum to better identify the wanted or unwanted frequencies. You must use a headphone to avoid feedback effects.
Ham Radio Operator’s: Just place your phone’s microphone close to your radio’s speaker and listen to clear audio in your headphone.
How to use:
DSP Audio Filter uses a waterfall to display the incoming frequency spectrum. With 2 sliders the cut-off frequencies can be adjust. The areas which are covered by a grey blurry layer are cut out and they will not be passed through to the headphone. All other areas will pass the filter.
The DSP Audio Filter can be used with 4 different sampling rates (22050Hz, 16000Hz, 11025Hz and 8000Hz) which can be set in the settings menu. Unfortunately not all devices support those sampling rates. The DSP Audio Filter will check for the supported sampling rates and only allows the selection of the supported sampling rates.