Do snakes have ears is one of those questions where the obvious answer and the real answer point in opposite directions. Look closely at a snake's head and you will not find ear openings, ear flaps, or eardrums on the surface — there is nothing like the visible ear you see on a lizard or a mammal. In that outward sense a snake has no ears at all, which is exactly why the old belief that snakes are stone deaf took hold.
But the absence of an outer ear does not mean the absence of hearing. Inside the head, a snake keeps a functioning inner ear: the cochlea and the balance organs that vertebrates rely on are still there, tucked away on each side of the skull. What snakes lack is the outer and middle-ear machinery that normally collects airborne sound and funnels it inward, so they simply receive sound through a different route than we do.
That route runs largely through the jaw and the ground. A snake's lower jawbone rests against the surface it is lying on, and ground-borne vibrations travel up through that bone to a small ear bone connected to the inner ear. In effect the snake 'hears' the footsteps of a person or a large animal as a vibration conducted through the soil, the floorboards, or a log — a sense of touch and hearing blurred together that is very good at detecting something heavy approaching.
Airborne sound is a weaker channel but not a closed one. Research has shown that snakes can detect low-frequency airborne sound to some degree, picking up the deeper part of a voice or a low rumble even without an eardrum, while higher-pitched noises mostly pass them by. So a snake is not reacting to your shouting the way you might expect; it is far more tuned to the thump of your weight on the ground than to the sound of your voice.
This explains a lot of snake behavior outdoors. A snake often 'knows' you are coming and slips away before you ever see it, not because it heard you call out but because it felt you walking. It also means stomping as you move through tall grass or brush is genuinely useful — those ground vibrations give nearby snakes ample warning and let them leave on their own, which is almost always what they would rather do.
Knowing how a snake senses you does not tell you which species just felt your footsteps and froze. That part — harmless rodent-hunter or something that warrants caution — is decided by markings, not hearing. If a snake holds still long enough to study, photograph it from a safe distance and let SerpentID compare its visible features against likely local species, then decide how much space to give it before you move on.