3-month birthday present

On Peter's 3-month birthday he got his Hearing Aids! I was shown how to clean them,and change batteries, which I was advised to do every Friday at least, even if they aren't completely used up, as he needs maximum power, good amplification to hear anything. All the buttons are deactivated so he can't mess with the settings, but that means I need to open the battery compartment to turn them off. The audiologist wanted to test the actual volume in his ear canal, but the tiny little tube wouldn't fit along with the ear molds, so for now they are set based on typical babies of his age and hearing loss. We will try that test a different time. Peter didn't (and doesn't) mind wearing his hearing aids, but he hasn't shown any major awareness of sound. I'm no expert in that area, though. What does a happy, extremely visually acute baby look like if he hears something? Maybe I will know more once therapy starts up again. Things I have learned in the last couple weeks of hearing aid use: 1) babies are moving targets and it is even more difficult to "aid" them as they naturally turn towards the side of their face that is touched 2) check the batteries! Not that they work, but that they are there...I opened (to turn off) one aid to find no battery, as he had knocked it free as I was putting the aid on hours before :/ 3) kangaroo position in the sling means less feedback than the sideways position 4) taking the HAs out for sleep means something like 5-10 times a day right now! 5) feedback is going to be a common noise until he can sit up by himself, as lying on a blanket, lying in the bouncer chair, lying in the carseat...lying down = feedback