You're subvocalizing, and yes, it's inefficient as far as speed goes (as far as comprehension goes, some may argue that "hearing" it increases comprehension).
If it's one thing I have to give credit as much as I put it down, the Evelyn Woods program helped me overcome subvocalization before I knew about photoreading. Getting over subvocalization will definately increase your speed...it's like this: when you see the word
apple
and you subvocalize it, you're really getting the word "ap-ple". But when you DON'T subvocalize it and practice, the word "apple" becomes a symbol, just like when you see a peace sign it means peace.
It's only a problem as far as speed goes, and my friend who subvocalizes claims if he didn't he couldn't remember his readings as well.
Of course, that takes into account he's never NOT subvocalized.
Since you wouldn't be PRing if speed wasn't a factor, I'm guessing you'd want to stop subvocalizing. I don't know exactly how to stop doing this, I just consciously avoided it with practice. The Evelyn Woods program taught this method:
With your right hand open and your palm down on the page, place your middle finger under the word you are reading. Then move your hand to the right, reading the words above it as you go along. When you reach the end of the line, slide your hand to the beginning of the next line and continue.
The point is that you follow the speed of your hand and NEVER backtrack...if you miss it, pick it up later. Your eyes are following the steady speed of your hand, not the other way around. This kinda forces your brain to keep up, kind of like jogging; your body adjusts to the oxygen usage.
Just don't get too dependant on this method. While it will help stop you from subvocalizing, your eyes move faster than your hands, and after you break the habit of subvocalizing you'll want to go faster than they can go.
-Ramon http://razor.ramon.com