This is an 60mm impeller air raid siren.
It is extremely loud. (120 dB from my smartphone app 'noise meter')
In this video, I throttled the motor just 30%. because I didn't want to be caught by the police.
So if you give the motor 100% throttle, it is louder than this video.
This siren is powered by a 2204 brushless motor (GARTT ML2204S 2300KV) on a 3S Li-Po battery and a 20amp ESC.
It has a 'Siren Base', so you can attach this siren you want.
It is assembled by 3mm screw.
Brushless Motor : http://www.aliexpress.com/item/GARTT-ML2204S-2300KV-Brushless-Motor-For-QAV-Quadcopter-Multicopter/32391141894.html?spm=2114.01010208.3.27.bo1F7l&ws_ab_test=searchweb201556_7,searchweb201602_2_10017_10034_10021_507_10022_10020_10009_10008_10018_10019,searchweb201603_6&btsid=251f7274-6331-4b6b-9ec5-f6a627297870