They need to use different equipment to alert themselves to different things. For example, they might have a bed shaker that is connected to the fire alarm so they know if there is smoke or fire. Instead of doorbells ringing they might have their phone vibrate or lights flash so they know someone is at the door. If they want to drive they might have special tools like things that sense if horns are going off to alert the driver. In cars, they have equipment that can alert the driver if there is a emergency vehicle like an ambulance or police car approaching. Deaf are actually usually better drivers because since they cant hear as well they are more focused and alert using their eyesight.
