My two kids' sleep have been interrupted by very loud shrill noise that seem to imitate bird calls. Sometimes It takes place in the early hours in the morning at 2am, 4am and 5am. In the afternoons, the noises start at 3pm and 5pm. It does not seem to be produced by real birds. It seems to me that it comes from a mechanical or electronic device.

According to a colleague of mine who had been living in the north of Thailand, the device produces loud, shrill noises to scare birds in rice fields. Expensive devices can project loud, shrill noises up to 500 meters in radius. They can be battery-operated (think lithium batteries) or powered by an electrical source.

Farmers occasionally use them to scare birds away.

Does anyone know what the device is?