To be clear, you are getting a beep that you do not want. Your OP said you wanted a beep. First reinstall Reaper. Second, are you running some software that beeps until you buy it like:
https://www.usb-audio.com/download/
At first it will run in demo mode and "beep" every 30 seconds. On buying it you'll get a personal unlock-key that turns it into a full version for Windows or a replacement driver for Mac respectively.
We encourage you to install the driver and have a try before you order.