It can be defeated by jamming the relevant frequency bands, i.e. by overlaying other mains recordings with random fluctuations. No deed to remove the original.
I'm not sure a notch filter would be enough because, even though the mains is supposed to be a perfect sine wave, some harmonics occur (sometimes with a much higher frequency). Perhaps by filtering all harmonics as well? Sound quality isn't exactly a must in these situations.
It requires a technically astute criminal, though, and most aren't.
It requires a technically astute criminal, though, and most aren't.
Exactly. Many don't even use gloves. I was wondering on how precisely you could locate the hum and if you could deliberately create a hum signature for a region.
I'm not sure a notch filter would be enough because, even though the mains is supposed to be a perfect sine wave, some harmonics occur (sometimes with a much higher frequency). Perhaps by filtering all harmonics as well? Sound quality isn't exactly a must in these situations.
It requires a technically astute criminal, though, and most aren't.