High-Pass Filter
From Audacity Development Manual
High Pass Filter passes frequencies above its cutoff frequency and attenuates frequencies below its cutoff frequency. This effect can therefore be used to reduce low frequency noise.
- Accessed by:
Sound below the cutoff frequency is not eliminated but increasingly attenuated as the frequency falls further below the cutoff. The steepness of the attenuation is set by the rolloff value. For example, with a rolloff of 6 dB per octave, the sound decreases by 6 dB for each octave below the cutoff frequency (an octave below is half the frequency).
Rolloff [dB per octave]
TBP
Filter quality [q] for 12 dB rolloff
TBP
Cutoff frequency [Hz]
TBP
It is hard to design a pass filter with a sharp cutoff, so the cutoff or corner frequency defines the point at which the audio is reduced by 3 dB. Thus there will also be a small and decreasing amount of attenuation just above the cutoff frequency.
To achieve more attenuation you can run the effect again or use a greater rolloff.
