Domestic internal alarms don't make a very loud noise. In our house we have a PIR-triggered external siren, 129db and difficult to get at. One of these in a hard-surfaced building will not only alert everyone nearby but more to the point it'll be pretty frustrating for the bad guys. It's quite difficult to think straight in high noise - the instinct is to get away from it. If the siren is fixed high up and behind wire mesh, with armoured power supply to it, it'd take a little while to disable (and not nice to stand in front of whilst doing that). 129db is pretty irritating but bearable for a short while if you don't mind hurting your ears. But two external sirens, at slightly different frequencies ... the dissonance would make a pretty shattering noise. Have some ear defenders outside in case you need to go in to turn things off.
Workshop security
in Tools and Fabrication
Posted
Domestic internal alarms don't make a very loud noise. In our house we have a PIR-triggered external siren, 129db and difficult to get at. One of these in a hard-surfaced building will not only alert everyone nearby but more to the point it'll be pretty frustrating for the bad guys. It's quite difficult to think straight in high noise - the instinct is to get away from it. If the siren is fixed high up and behind wire mesh, with armoured power supply to it, it'd take a little while to disable (and not nice to stand in front of whilst doing that). 129db is pretty irritating but bearable for a short while if you don't mind hurting your ears. But two external sirens, at slightly different frequencies ... the dissonance would make a pretty shattering noise. Have some ear defenders outside in case you need to go in to turn things off.