A notch filter, also called a band-stop filter or T-notch filter, and the opposite of a narrow band-pass filter, is an electronic filter typically used when the high frequency and the low frequency are less than 1 to 2 decades apart (that is, the high frequency is less than 10 to 20 times the low frequency).
In the audio band, a notch filter uses high and low frequencies that may be only semitones apart.
Example 1: Anti-hum filter
- Low Freq: 59 Hz
- High Freq: 61 Hz
- this means that the filter passes all frequencies, except for the range of 59-61Hz.
Example 2: Anti-presence filter
- Low Freq: 1000 Hz
- High Freq: 4000 Hz
See also
