The Boost Fin doesn't make any loud noise. We tested it out with surfers paddling 3ft away from the Boost Fin and they couldn't hear a thing. All they did was wondering how the heck was that surfer paddling so fast! Later tests determined that sharks are attracted by frequencies ranging between approximately 10 and 800 Hz while we are using 30Mhz which equals 30000000 Hz. Plus you can also use a Shark Band bracelet for extra safety.