Matching the noise to the bird’s behavior is key. There are two types of sonic devices: alarm/distress calls and frightening noise. Distress call devices mimic the bird’s natural communication sounds. Birds relay information on dangerous situations to the rest of the flock through use of distress cries; these electronic bird repellers broadcast a copy of this distress cry to scare the flock away. Since these sounds are species specific, you must buy the correct distress call for the type of birds you are handling. Irritating noise devices on the other hand, work by making loud, random noises that annoy the flock. Zon canons, air horns, gun shots and simply banging pots and pans together are all examples of frightening noise devices.
For sonic devices to be effective, they should be used in conjunction with visual devices and timed to the bird’s behavior. This means you should wait until the flock is returning to their roosting spot in the late afternoon and then hit them with an overload of noise, distress calls and threatening movement. It may take several days to move the birds. A common mistake is to leave the noise devices constantly on; this allows the bird to realize that the noise is not paired to their behavior and not a threat to them.