People born deaf do not think like we think. They don't hear voices and words as we do when we think to ourselves. They more see "words", or like lips moving.
As I said in the comments,
Satan "whispers" to us (deaf or not) by the means of thoughts. It's in a level that is within us, as referd to "hearts" in the following verse.
So have they not traveled through the earth and have hearts by which to reason and ears by which to hear? For indeed, it is not eyes that are blinded, but blinded are the hearts which are within the breasts. 22:46
Also thoughts can take many forms.