Is it harmful?
The maximum volume of the Mosquito at one metre is 104 dB. Units are typically mounted above four metres, so the maximum volume at the ear is 97 dB, and at maximum range, significantly less and no launder than other sounds in our environment. The effect is achieved by the sound being repetitive and highly annoying at low volume levels.
The Mosquito is safe, legal and harmless. The safe use of the anti-social device to prevent unwanted behaviour is backed by several organisations. Here you can download and view various documents that verify its use in terms of its legality and harmless nature when installed in appropriate situations.