Alarms - motion sensors

[Richyboy]

House came with alarm system installed. When the alarm is not armed every time you walk in a room the motion sensors makes a slight clicking noise (almost like the press of a Casio digital watch beep plus a click), is this normal? Installer charged me a call out charge to come round and tell me it's normal but I've got sensitive hearing and its pissing me off. I'm told it's all hardwired so it's not a problem of low batteries as I first thought.

[Richyboy]

The alarm guy said it was a click, but I don't think there are any moving parts. To me it sounds similar to a digital watch beep. Its a honeywell console.

I guess changing the PIRs is the only option. These are the PIRs I have at the moment: