Hi, I am an Independent Advisor, and welcome to Microsoft Q&A.
I understand your Desktop PC is making a clicking noise at irregular intervals.
Since you have mentioned that you already turned off the speakers and you are still hearing clicking noises, this may be related to internal parts of your computer.
Clicking sounds can be caused by your hard drive (Disregard if you are using SSD), Fans, Power Supply Unit, or other moving parts in your PC, like your DVD drive.
Run a diagnostic test on your computer.
If you didnt get any error on the diagnostic test, you will need to physically identify where the noise is coming from, I suggest opening up the tower, but if you are not comfortable with removing any parts of your machine, you can take it to a professional hardware technician, or contacting the warranty hardware support of your computer.