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This java applet is a demonstration of digital filters. You should hear a noise waveform when the applet starts up. If you get a message "Need java 2 for sound", then you should get the Java plug-in.

The applet starts up with a low-pass filter. It shows the frequency response of the filter, the spectrum of the filtered waveform being played, the waveform itself, and the impulse response of the filter. Click on the response curve to change the cutoff frequency.

You can use the popup menus on the right to select another filter or input file.

Full Directions.

Windows/Mac version

The source.

More applets.

Zip archive of this applet.

Version 1.2d, posted 4/21/14

Thanks to the JavaZOOM team for the mp3 code.
Thanks to Digital Droo for the Monkey Developers sample.
Thanks to Søren "Jeff" Lund for the Arabian Bias sample (and also to the HVSC team and Andreas Varga).

Thanks to Tory Esbensen for the speech sample.
Thanks to the MAME team (and Eugene Jarvis and Larry Demar) for the Robotron sample.