Combining hum removal, buzz removal, brickwall filtering, and spectrum analysis into one easy to use plug-in, MR Hum is the perfect tool to clean up recordings with any sort of hum or nasty buzz.
The hum removal section works by applying a set of notch filters spaced at multiples of the fundamental hum frequency, usually 60 Hz or 50 Hz. You select the fundamental frequency, the number of harmonics you want to eliminate (up to 10), and the width of the notches (the default works fine). There are presets for the usual cases of 60 Hz hum and 50 Hz hum. You can also select any fundamental frequency continuously from 20 to 200 Hz. Sometimes it’s necessary to use a slightly different frequency in cases where the hum has been recorded on analog tape and played back on a different machine, which will cause the hum frequency to change.
The high resolution spectrum display makes it easy to see the hum frequency and the number of harmonics that are required. The spectrum display can run before processing, to see the input signal spectrum, or after processing, to see the output signal spectrum. The monitor feature allows you to hear the signal being removed, offering another way to set the parameters.
MR Hum contains a separate processor for buzz. Buzz is a periodic signal with frequency harmonics through the entire audible spectrum, which would require hundreds of notch filters to eliminate. The buzz algorithm uses a different approach which is far more efficient. Often buzz is a nasty case of hum, and hence is at 50 or 60 Hz, but sometime buzz is caused by a motor or some other kind of interference, hence the buzz processor allows any frequency from 20 to 200 Hz.
Finally MR Hum also provides brickwall filters to eliminate low or high frequency interference.