good questions. i haven't personally measured, however, these machines are very well documented.

i believe the average power consumption is less than ~60W for the optiplex 390 i've listed. it's max total power is 235W. newer machines are usually more energy efficient.

it appears the sound level is around 23dB from the bystander position for machines placed on a table-top.

source: https://i.dell.com/sites/csdocuments/Shared-Content_data-Sheets_Documents/en/Optiplex-390-Technical-Guidebook-101311.pdf

hope this helps!