I have just bought a secondhand iPhone 3G , unlocked with Yellowsn0w, running firmware 2.2.

All seemed perfect however when making a call, the sound coming out from the receiver is very poor. Like a vibration or reverb in the voice......

Switching to Speaker it's fine, nice and clear, but when back on the receiver earpiece it is back to the poor sound quality, far from good clarity.

Could this be a software issue or more likely the receiver is faulty??

Anyone else heard of this problem?