Music and Computers

Hearing Different Filters

Filters modify a sound by letting some frequency components pass through easier than some others. For example, a low pass filter lets low bass frequencies pass through, but filters out higher frequencies. This is similar to the bass control on a stereo.
In this Applet, you can choose various source signals like sine waves, sawtooth, etc. You can also select different filters and hear the effect of changing their frequency and bandwidth.

To Do:

  1. Select WhiteNoise from the "Source" menu below. Select "LowPass" from the "Filter" menu below.
  2. Change the "Frequency" of the filter. Hear how it reduces the high frequencies above the cutoff frequency.
  3. Increase the "Q" value and listen to the filter resonate.
  4. Change the source to the SineWave and then sweep the source frequency from low to high using the fader. Hear the loudness change.
  5. Change the source to the Impulse and set the source frequency to about 300 and the source amplitude to about 0.5. Set the filter Frequency to 3000 and the Q to 8 and notice how the filters "rings" when hit with an impulse. This is called the "Impulse Response". How does changing Frequency and "Q" affect the impulse response?
  6. Experiment with the various filters.
  7. Select the BandStop filter and the SineWave source. Sweep the SineWave frequency past the filter frequency. Note how the sound disappears when the frequencies match! Change Q and notice that the width of the band where the signal disappears changes.