The Health and Safety (Safety Signs and Signals) Regulations also set standards for acoustic signals. Audible signals need to be set at significantly higher frequency than the surrounding noise level. A 10 dB (decibel) higher setting is recommended. Thereby indicating a greater degree of danger or a more pressing requirement action. It must be ensured that at that level it doesn’t become excessive and/or painful.
Acoustic signals should be readily recognisable and distinguishable from other signals and alarms, in their pulse duration and sounding pattern. Furthermore, acoustic signals should be used on their own; and not in combination with other sounders, alarms and sirens to avoid confusion. Devices which produce signals at variable frequencies are favoured over those that can only produce a constant frequency.