NoHum

It's an application that filters the signal using spectral subtraction, which is a popular technique in the mobile phone industry.

Although the filter introduces some artifacts of its own, it is a great improvement over the torture of inducing a constant hum into one's ears.

The filter performs well as long as the noise signal is reasonably clean, one that sounds like hum. A more distorted signal, normally referred to as buzz, with large spikes and discontinuities has proved harder to suppress. Your mileage may vary.