FilterOne may remove certain areas in a (lenke) spectrum (bass, for example) using a filter, and let other areas pass through. Bass and treble controls on a stereo system are filters. There are several types:
A lowpass filter lets the bass tones through (the low frequencies) and removes the treble (high frequencies). The separation between low and high frequencies is called the cut-off frequency. If the cut-off frequency is 500 Hertz (Hz), all of the frequencies over 500 Hz will disappear.
Click here to listen to a lowpass filter on a string sound, and here to listen to a lowpass filter on a voice!
A highpass filter lets the high frequencies through and removes the low.
Click here to listen to a highpass filter!
A bandpass filter lets through only a small frequency area surrounding a center frequency. Click here to listen to a bandpass filter!
If the center frequency is shifted up and down we get an effect that is called wah-wah. Klick here to hear wah-wah!
A bandstop filter removes a small frequency area surrounding a center frequency.
Frequency determines the cut-off frequency (for lowpass and highpass filters) or the center frequency (for bandpass and bandstop filters).
The Q factor determines how narrow the frequency area will be (for bandpass and bandstop filters). This value may also be increased to provide extra emphasis on the area surrounding the cut-off frequency.
Filters are often used in sound processing. If you send your voice through a bandpass filter with a center frequency of 1000 Hertz, it can sound as though you are speaking on the telephone. Experiment a little with the Q-factor!
Click here for an example. You can make white noise with the Whoosh program, and send the sound through a wah-wah. Click here to listen to the wind sound it makes!
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