Why does my Galaxy S3 make a noise when I put it down? Occasionally, when I put my Samsung Galaxy S3 down relatively firmly, it makes a noise that's sort of half way between 'BONG' and 'CLANK'. When it happens I can immediately pick it up and put it down again to make it happen again. I can repeat this for as long as I like. Pick up, put down, BONG/CLANK, repeat.

There are no on-screen messages, just the noise. Why is it doing this? Can it be stopped?

Thanks
Well, I've figured it out. Sort of. I habitually put my phone down on top of my wallet, which contains my NFC-chipped credit card. It turns out the phone actually makes that noise when it finds an NFC chip. If I push my credit card against the back of the phone the same thing happens.

I'm still not sure what it really means, though.