I hear some brief "clunky" (?) sounds and then what seems to be fans spinning up.
Update your post to include full system hardware specs and OS information.
PSU: make, model, wattage, age, condition?
Disk drive(s): make, model, capacity, how full?
Are you comfortable with powering down, unplugging, and opening the case in order to locate the source of the sound? Do you have a family member or friend who can help?
Use a rolled up sheet of paper or a long cardboard tube held to your ear and carefully listen about to locate the source of the sound.