Unless you can make a recording of the sound, upload it to some file sharing "cloud" storage space, share the file, and include the share link in your next post, I suggest that you take your 10-year-old computer to a local independent computer repair shop. I suggest avoiding consumer electronics stores, office supply stores, and any other large establishments whose primary business is something other than computer repair.
That said, if you're hearing "beeps," that's generally indicative of a hardware fault. Different systems will have different patterns of the beep sounds for different error conditions. See, for example, https://www.computerhope.com/beep.htm