Ground interference on audio track after pluggin my DV camera to the wall's power out

[charge]

How do I remove this bass type of sound from my video recording's audio track? I went through Sound Forge's menu items, but couldn't find a tool for removing this. Anyone?

Also, why did this occur? I used the cheap table mic that is used to speak on MSN etc. As long as I recorded on battery, there was no interference. Is it because I used an external mic?

[redsox_mark]

If it is a very low frequency bass sound, you can use a filter to cut out all the audio below a specificed threshold on most editors. But of course you will lose any "real" bass as well.