Are Alarm Sirens Necessary With Modern Alarm Systems?
Are Alarm Sirens Necessary – Is it acceptable to disconnect an external siren from an alarm system if the alarm is causing issues with disturbance or if there is no location for the device?
Does this advice conform with what’s laid down in the Australian Standard? In SEN’s opinion, do internal and external sirens have a purpose in modern alarm systems, given layers of notification?
A: The Australian Standard’s (AS 2201.1 1998) Signalling Systems Section is the one applicable here. Of most relevance to this discussion is the fact that Section 6.2 of the standard notes:
“Some local ordinances may not permit audible alarms and others may impose limits on durations or limits on the sound level different from those specified (in the standard)”.
This is essentially an acknowledgement that local rules governing noise pollution take precedence over the stipulations of the standard in relation to the use of audible alarm signalling equipment. Taking this into account, any false alarm accompanied by an audible siren that generates a complaint actioned by police could also be considered limited by local ordinance.
More telling is that the standard defines categories of signalling on a scale of performance with Category A involving transmission beyond the client’s premises and Category B involving audible signalling at the client’s premises.
We’d argue that so long as the communications connection is functional (Category A), then activation of a local siren in accordance with Category B (especially if it occurs after repeated and unresolved nuisance alarms) is a breach of local ordinances that would be considered by police responding to a noise complaint to be unnecessary.
The broader question is whether internal and external sirens have a purpose in modern alarm systems. Even if you don’t install an external siren, most alarm hubs or keypads have an audible siren that’s plenty loud enough to see off an intruder without creating noise pollution on the street. Note this would likely not apply in strata applications.
Further, evidence with our own systems, supported by CCTV footage, indicates that intrusion events generating a siren typically cause the intruder to beat a retreat. Evidence suggests this response to a siren occurs even if the person is on site for a legitimate purpose – they will typically retire and attempt to contact building owners to explain their presence.
On a number of occasions, we’ve observed unexpected and unidentified visitors entering a property and approaching buildings but turning back after activating the external alarm sensors. While the impact we see is psychological there is a deterrent effect that is worth having.
We’d argue that the longer your expected response times, the earlier the siren should sound – that means when a designated perimeter is breached at a point before the intruder arrives at buildings.
You’d be managing this with externally-rated wireless sensors – that means IP55 or higher – preferrably with sunshades and installed without too much moving vegetation or thermally active surfaces in their angle of detection.
You can see some external alarm sensors here and here and here or read more SEN news here.
“Are Alarm Sirens Necessary With Modern Alarm Systems?”
