Snakes are by no means deaf. They hear noises just like us but cannot decipher most sounds and generally everything seems mumbled to them.
Unlike humans and most animals, snakes have inner ears but no outer ears. That simply means that instead of the big floppy pieces of cartilage that we carry on our heads is not on theirs.
Basically, a great way to hear like a snake would be to put your thumbs over your ears and have someone talk or yell at you. You can hear them, but you cant decipher what their saying. In this sense, snakes can respond to thuds, loud cracking noises or low rumbling noises better than other sounds.
Another thing to take into account is to NEVER EVER put your snake cage next to, around, or near a TV or sound system because snakes can sense vibrations with their bellies also. Almost like how Native Americans would put their ears to the ground to hear a buffalo herd, so do snakes. The constant sound of television or stereo will drive them crazy (not really, but I'm trying to put it simply) and will seriously lead your snake to a stressful life resulting in a shorter, less fun life.
So no, snakes are not deaf.
Yes, they can hear.
and yes they technically have ears, but we cant see them.
Hope that helped!
Reptile keeper, breeder and enthusiast