I don't believe it is required.
A.6.9.3.1 Audible alarms are normally located on the outside of the building. Listed electric gongs, bells, horns, or sirens inside the building, or a combination of such used inside and outside, are sometimes advisable.
Outside alarms can be omitted where the sprinkler system is used as part of a central station; auxiliary, remote station, or proprietary signaling fire alarm system utilizing listed audible inside alarm devices.
A.6.9.3.2 All alarm apparatus should be so located and installed that all parts are accessible for inspection, removal, and repair, and such apparatus should be substantially supported.
The water motor gong bell mechanism should be protected from weather-related elements such as rain, snow, or ice. To the extent practicable, it should also be protected from other influencing factors such as birds or other small animals that might attempt to nest in such a device.