Volume bar at the top of screen

The volume bar does not normally appear.

You need to tell us more about your exact scenario - what you're doing when this bar appears, how frequently it appears, any accessibility settings you may be using, iOS version, etc.

No, as I stated in my initial message they are both iPhones 12 Pro Max, not iPads.

My volume bar appears on the left side of the screen on my iPhone 12 Pro Max but the volume bar appears on the top of the screen on my wife's iPhone 12 Pro Max. Why would that be? Can the location of the volume bar be changed?

Both of us updated to the current iOS 17.4. The volume bar appears on all of our open pages when we either raise or lower the volume, but my volume bar appears on the left side of my screen. On my wife's iPhone, when she either raises or lowers the volume, the volume bar appears on the top of her screen. I am aware that it disappears but this is how the volume bar appears when we raise or lower the volume. As for accessibility settings, I 'm not sure what you are looking for. I haven't changed those settings since we have owned the iPhone. Our settings are identical.

The response provided above applies to you as well.

Do you and your wife have different iPad models, perhaps with different screen sizes?

Might one iPad be in landscape orientation while the other is in portrait mode?