Why do some iPhones have a low battery sound? You guys have never heard of this before. Most of you at least. I own 2 iPhones bought in a legitimate Chinese Apple store. Whenever I use it, they would make a tri-tone dying robot low battery sound at 20% and 10%. This will sound even if you're on silent. So to turn it off (you can't) you'd have to change your ringer volume. There are no apps causing this since I wiped my phone and it still happens. I would like to make a conclusion that only Chinese iPhones have this stupid tone.

Why did they put that on these phones and not American ones?
The app "Battery Alert!" will allow you to change several battery related sounds (warning, alert, and full). It is currently $.99 USD on the app store.