I have both an iPhone 5 and an iPhone 4. Both are on iOS6, but I have a sound problem on my iPhone5. It's keyboard clicks (sounds) are very low in volume. Sometimes the problem disappears, and sometimes the problem comes back. I have verified that this problem does not exist on my iPhone 4.
All volume controls are maxed out, and I do not have anything blocking the speaker.
Everything sound effect works at my set volume, except the keyboard clicks.