For those you wanting to test your Nexus 4 for the buzz sound but do not have service yet; get a voip app of some kind from the play store (I used sidecar, great app by the way) and make a call to this number using it: 909-390-0003
It is an echo back number. It rings once or twice then you talk and it echos back your voice. Beware though that any brushing or blowing on the mic winds up sounding like a buzz so if you think you have a buzz noise make sure you aren't blowing or brushing the mic. I did and I thought it was a buzz but I realized I had blown in the mic a bit.
Based on what it sounded like, I don't think I have the buzz sound.
Is the buzz sound very common with the nexus 4? It seems like it isn't extremely common and a lot more people don't have it than do like it was a small defective batch.