Audio filters are electronic circuits that are designed to either amplify or attenuate specific frequency range elements. When this happens, unwanted noise is removed from the audio signal, enhancing the tone of the output audio signal. Audio filters are essential in any audio system and they are widely used in both audio electronics and telecommunications.
There are several types of audio filters, including equalizers and crossovers. Audio equalizers are electronic filters that are capable of amplifying the audio signal according to a frequency-dependent function, whereas audio crossovers are electronic filters that split the input audio signal into different frequency ranges.
There are two main types of filters: passive and active. Passive filters don’t need a power source in order to operate properly, whereas active filters require a DC power source. Both passive and active audio filters are typically used in electronic components. Both passive and active filters can be subcategorized as follows: passive high pass filter, active high pass filter, passive low pass filter, active low pass filter, passive band filter, active band filter, passive band stop filter, and active bandstop filter.
Another common way to classify audio filters is regarding their frequency response. This classification goes as follows: high pass filter, low pass filter, bandpass filter, bandstop filter, notch filter, all-pass filter, and equalization filter.
High pass filters are capable of passing all frequencies above its cut off frequency while blocking all frequencies that lie below the cut off frequency. Low pass filters are capable of passing all frequencies below its cut off frequency while blocking all frequencies above it. Bandpass filters are capable of passing all frequencies except those ranging between the lower and the higher cut-off. Notch filters have a very high quality because of its extremely narrow stopband. All pass filters are capable of passing all frequencies while altering the phase relationship between them. Finally, equalizer filters are capable of amplifying frequencies according to frequency-dependent functions.