Hum, Rumble, and similar low-frequency noise, can be reduced using the DeNoiseLF application.
Why DeNoise is not the right tool
DeNoise is a spectrally-based method, dividing the audio into 1024 frequency bands at the rate of 80 overlapping frames per second. For CD quality sound, each band has a width of about 22Hz, too coarse for the accurate resolution of low-frequency noise. In particular hum, which is at a fixed and sharply defined frequency, cannot be treated this way. Improving the frequency resolution would require dealing with frames in the order of 1 second length, whereas the effective treatment of hiss and similar noise demands a frame rate in the order of 80 per second.
How DeNoiseLF works
DeNoiseLF is not a spectrally-based method. It makes extensive use of wavelets to extract and treat the low-frequency audio content in a manner which achieves perfect reconstruction of the untreated higher-frequency content. The noisy audio signal is assumed to consist of the desirable audio and the undesirable low-frequency noise, simply mixed. Advanced statistical algorithms are used to estimate the two streams and remove the noise. The DeNoiseLF interface permits you to view both wave-form and spectral information about the audio and the treatment.
Broad-band noise versus Hum
DeNoiseLF has two mutually exclusive modes of operation.
• A "General" mode suited to the reduction of noise which is widely dispersed across the low-frequency spectrum.
• A "Hum" mode for the reduction of noise at a sharply defined frequency – however DeNoiseLF is not a notch filter.