Strange noise from APC?

[sngraphics]

When I turn on my MacPro that is connected to my APC SMX1000, or when I wake it up a sudden and strange noise comes from the APC.
It is like a metal sound popping or like metal hitting against metal is this a problem or a normal function when a sudden load hits the APC?
Any info would be much appreciated because I can still return this unit if I have to.

 

[hfg]

That does sort of sound like what my SmartUPS 1500 does when it goes into "self test" mode every few days. It scares my dog!

My guess is that your 1000VA UPS can't handle the startup surge of a Mac Pro and thinks the power mains have failed and briefly goes into the full operational mode. May also happen when waking from sleep. You might want to consider a slightly more powerful UPS for the Mac Pro. They should normally be perfectly quiet when the UPS is on standby.