I seem to recall the jet plane sound that often came from my machines
would cease when I put them to sleep/standby mode.

I have large 120mm fans that run very slowly, so there is almost no sound
from the computer even when it's running normally. The only time I hear
anything is when I push it really hard and the fans speed up.

Sometimes I can hear my data hard drive spinning up, but my other two
drives are SSD's and are completely silent also.

Anthony Watson
www.watsondiy.com
www.mountainsoftware.com