I have just started learning speed reading (in hopes of being able to rapid read faster). One of the things I've learned so far, is how to stop subvocalization. I haven't stopped it fully, yet, but hey I just started.
Try counting from one to ten inside your head while reading. This will force you to learn to read without subvocalization because you must see the words as "images", instead of words. And because your mind is "thinking" of something else (counting), you are forced to read without subvocalization. Hopes this helps some.
