Is Echo & "pixelated" garbled audio (intermittent) a HARDWARE problem?

[pcguys]

I have 3 galaxy S3's. It only happens on mine. Other ATT peeps say they never have that problem (but they are iphone ATT).

ATT offered to refurb hardware swap the unit.

I initially hesitated because they didn't do ANY trouble-shooting, and re-setting up a phone is a hassle, but ultimately, I decided to do the swap because I was 9 days out of warranty, and if I delayed further to further trouble-shoot, I might miss the opportunity. If it really is hardware, I certainly want it swapped out.

So, is what I described likely hardare?

Aren't there logs or some kind of diagnostics that could have been consulted to trouble-shoot this?

Thanks,
Mike