BR1500MS -Sine Wave 900w

[BillP]

Hi,

I've recently bought this unit and noticed that during operation it constantly creates intermittent squealing sound 2-3 mins after powering on in either loaded or non-loaded state. It seems to me that APC quality is going down the drain like most consumer electronics these days...

While rather quiet it drives me nuts when I try to work in total silence. I've recorded it below and attached here. 

Any ideas? Is this considered the norm? 

Thank you.

https://drive.google.com/file/d/1Al-DDNwPeIn_gnzQbdVUYt4moHtJmsel/view?usp=drivesdk