My little boy Andrew has just been fitted with hearing aids.
He failed the newborn hearing test (done just before he was discharged from NICU) and subsequent testing showed that his auditory nerve hasn't formed properly (sensori-neural hearing loss). He may also have conductive hearing loss, they don't really know.
Testing at this age (1yr+) seems to be based on behaviour and responses to sounds, he's not performing very well at the tests and they have set his first aids to quite high a level.
However, with or without the aids he seems to be very intermittent with his responses. Sometimes he will respond to us calling him, other times he won't. He doesn't startle to loud noises at all. And naturally his speech development is delayed - but the specialists aren't worrying about that until they can help his hearing loss.