What device serves as an audible alarm notification powered by water in a sprinkler system?

The device that serves as an audible alarm notification powered by water in a sprinkler system is the water-motor gong. This device works by utilizing water flow from the sprinkler system to create sound. When water flows through the pipe due to a sprinkler head being activated, it spins a water motor, which in turn strikes a gong or bell to produce an audible alarm. This is an effective method for alerting occupants and responding personnel that the sprinkler system has been activated, indicating a potential fire situation.

In contrast, a flow switch is an electronic device that detects the flow of water and can activate an alarm or a monitoring system, but it does not produce sound on its own. A pressure gauge measures the pressure within the sprinkler system but does not serve any notification purpose. A siren system may be used in some fire alarm setups but is not specifically powered by the water flow in a sprinkler system. Therefore, the water-motor gong is the correct choice as it directly handles audible notifications as a result of water flow.