55WRX

The alarm on my car went off in the early hours last night but it was very quiet - barely audible, but the lights were flashing. I've had a look at it this afternoon and with the limited information I have from the user manual everything seems ok.

Does anybody know if there is a setting for the alarm on a 2005 WRX which controls the volume of the siren? There's no mention of it in the alarm handbook, only the volume for door open bleeps. I'm going to call the Subaru dealer tomorrow, but if anyone has any info in the mean time it would be much appreciated.