My wife just got a new 5c. The sound volume was very low. I checked all the sliders and buttons, but everything looked ok. She has excellent hearing. It sounded to me to be about half the volume of my 5. And I don't think it's loud enough. After some research, I discovered that turning on Hearing Aid Mode in Accessibility increases the volume. That worked great for her 5c. I turned it on in my 5 and got better sound. Doing this will disable Phone Noise Cancellation. But both the top and bottom speakers have better sound. I hear who I'm talking to better. This may not be for everyone. But if your hearing is a bit off, you might try it.
Sent from from my iPhone 5
Sent from from my iPhone 5