A filter changes the frequency makeup of a sound by making parts of it weaker. Filters allow you to focus on parts of a sound that are of interest to you, or to take away parts that you don’t like, such as noise or ‘hiss’
(Some filters, also known as Equalisers, can make parts of the sound stronger).
Filters have two main controls:
- Frequency: the frequency at which the filter operates.
- Quality: the width and shape of the filter (narrow or wide / gentle or steep).
There are several types of filters:
- Low-pass filter – Allows all frequencies lower than its cut off point to pass (for example, if the cut-off frequency is set at 500 Hertz (Hz), all of the frequencies over 500 Hz will disappear). Does not allow any higher frequencies to pass. Best used to remove unwanted high sounds, or to highlight only the low frequency portions of a sound.
- High-pass filter – Allows all frequencies higher than its cut off point to pass. Does not allow any lower frequencies to pass. Best used to remove unwanted bass sounds, or to highlight only the high frequency portions of a sound.
- Band-pass Filter – Allow one band of sound to pass through. Best used to highlight frequencies of sound in a specific area. The Quality of the filter will affect its width.
- Band-reject Filter – Will not let a certain band of sound to pass through. Best used to remove sounds at a specific frequency. The Quality of the filter will affect its width.
The bass and treble controls on your stereo are filters.