SUWON, Korea — Do you like your phones LOUD? Then maybe you should get a Samsung Galaxy S5 designed for a Chinese wireless carrier.

On a small-group trip to Korea in advance of the Galaxy S5 launch, Samsung took us on a tour of the company's testing labs, where the company makes sure new designs perform up to snuff. I saw a bunch of unreleased and barely released devices being put through their paces as robots pounded their buttons, they got hoses of water sprayed on them, or they were locked in little boxes full of fine, white dust.

But I knew about all of that before. The news to me was what Samsung does with call quality, and it blew my mind.

Deep within Samsung's testing lab at its Suwon, Korea headquarters are a number of studio booths that look like the kinds of place you'd record a radio commercial. In each one, Samsung can summon background noise and voices from different countries – because they're different! Chinese people like their phones loud, for instance. In the U.K., they want more bass tone in their voices. Americans like more treble. (They're right; I do.) The background noise of two-stroke motors in India requires different noise cancellation settings than the hum of American traffic.

I mean, I knew that phones from different countries had different radio bands, but audio tunings? Wow.

Alas, Samsung can't do all of its testing at home, thanks to U.S. carriers. They trust no one. So while Samsung tests its prototypes up to specific U.S. carrier specs and standards – and yes, they each have different standards, posted on the wall in the test lab – the phones then have to be sent to third-party labs in the U.S. to be double checked. Some other global carriers allow Samsung to certify phones, which is why some devices may come out elsewhere first.

I've been to cell phone testing labs before, at Chinese mobile manufacturers and U.S. carriers; Samsung's setup was the brightest, cleanest, and most extensive I've seen so far. Take a look at the slideshow to see how Samsung tests its prototypes.