Audio Not Clear in AVI

[abdul_sma]

I had downloaded an movie in MP4 format and converted it to AVI using Xilisoft. In the MP4 the audio was clear.After conversion i deleted the MP4 and when i played the AVI file the audio is not proper.I am getting some background sound from the start and its there throughout the movie.
Is there anyway to fix this issue.

[Baldrick]

Maybe with an audio editor like goldwave, audacity and some remove noise filters. I think you can import the avi directly and it will open the audio part in those tools. After you tried fixed the audio save as a mp3, add the new mp3 with the old avi using avimuxgui.

But what kind of background sound is it?

[abdul_sma]

some kind of a buzzing sound which is very loud