they hear in a really cool way. mammals like humans hear with tiny little hairs in their inner ear that vibrate in response to disturbances in air, aka sound. spiders have tiny little hairs on their legs that also move in response to air disturbances, and this probably also gets processed as something like sound for them when the signal reaches their brain. odds are mammals just can hear more clearly
deaf people can also kind of "hear" in a sort of similar way by equipping special backpacks/chestplates that move in response to audio (for example, a music record can be fed into it as a signal). this vibrates their bones and the bone vibrations get interpreted as something like sound. if they're in a club with loud music and a good bass/sub-bass system they can also feel the lower frequencies since their bones will vibrate from that as well
