Hearing dog

A hearing dog is a specialized assistance dog specifically selected and trained to assist people who are deaf or hard of hearing by alerting their handler to important sounds, such as doorbells, smoke alarms, ringing telephones, or alarm clocks. They may also work outside the home, alerting their handler to sounds such as sirens, forklifts, and a person calling the handler's name.

Text from Wikipedia, CC BY-SA 4.0