Sound quality

[scaner]

I have my Motorola droid for 4 months and never have a problem with them,but now i have weird crackle at higher volumes when i speak on the phone but the if i move to the speaker-phone its work ok,its like a metallic sound when i talk,if i lower volume down its gone,can somebody help me or tell how to fix this,or somebody have the same.Thanks Droid_family.