EchoFilter uses the soundcard of a pc to process audio signals in real-time. The latest version incorporates a powerful programmable audio filter as well as a frequency counter up to 16 kHz with a 8 Hz resolution. The filter bandwidth can go down to 20 Hz and can extract signals and sounds from the audio signal that may normally be close to inaudible. Is can also be used the remove noise and unwanted sounds form the audio signal. The real-time spectrum analyzer and spectrogram gives the user an excellent visualization of the audio. The program also includes an automatic gain control, frequency shifting, graphic equalizer, audio compressor and expander, wave file player and recorder and noise reduction filters. Visit the EchoFilter homepage for more information.