Why is my iphone automatically lowering ringer & incall volume settings?

Question

My wife and I purchased our iphones from two different AT&T stores. The volume setting keeps lowering itself to the lowest setting for both the ringer and in-call conversations. I actually saw it in action the other day. I looked at the screen and the ringer icon appeard showing full volume. Then it automatically lowered itself, deleting the small white square (that indicate volume setting) from right to left until there was only one square remaining on the left.
Does anyone know what is causing this and how to fix it?

Answer 1

I think it has something to do with "Sound Check" ... There's a setting under iPod with an On/Off slider labeled Sound Check. The manual describes it as "Set iPhone to use the iTunes volume settings" (p.65).
I had a problem where, the volume level would drop down by itself to a very low level, making my ringer sound barely audible. I was missing calls all over the place! Well, it turns out that in iTunes > Preferences > Playback, there is a "soundcheck" check-box. Soundcheck apparently adjusts the volume of your computer so that one audio track sounds as loud as another, even if they were recorded at different levels.
My theory, which I'm still testing with my iPhone (so far so good!), is to uncheck Soundcheck in iTunes, and turn off the on/off slider for the iPhone's iPod Soundcheck setting. What I think might be happening is that something about Soundcheck on the iPhone is not working right, perhaps the Soundcheck thinks the iPhone stock ringer tones have a sound level that is way top high, and so Soundcheck is compensating by setting the volume level on the iPhone super-low.
And with Soundcheck off in iTunes and on the iPhone, I'm not noticing any volume issues ... if the volume of some podcast is too low, I manually turn up my laptop or iPhone volume, big deal!
This may be a situation in which an automatic feature designed to eliminate the need for the user to do something that is not a big bother anyway, causes more unexpected problems than it solves.
So, so far, this has worked for me, but I want to give it a few days just to make sure something else isn't also in play. I'd love to hear if my theory and turning off Soundcheck everywhere solves the volume-level-drops-by-itself-on-the-iPhone mystery!