Random knocking sound in sleep mode

Hi TCHolt,

To clarify, is the sound coming from the speakers? If so, check your output settings with the help of the guide here: Change the sound output settings on Mac

You can also test the issue while logged into a new user account. Set up users, guests, and groups on Mac

"Add a user

1. On your Mac, choose Apple menu  > System Preferences, then click Users & Groups .
2. If the lock at the bottom left is locked , click it to unlock the preference pane.
3. Click the Add button  below the list of users.
4. Click the New Account pop-up menu, then choose a type of user.

• Administrator: An administrator can add and manage other users, install apps, and change settings. The new user you create when you first set up your Mac is an administrator. Your Mac can have multiple administrators. You can create new ones, and convert standard users to administrators. Don’t set up automatic login for an administrator. If you do, someone could simply restart your Mac and gain access with administrator privileges. To keep your Mac secure, don’t share administrator names and passwords.
• Standard: Standard users are set up by an administrator. Standard users can install apps and change their own settings, but can’t add other users or change other users’ settings.
• Sharing Only: Sharing-only users can access shared files remotely, but can’t log in to or change settings on the computer. To give the user permission to access your shared files or screen, you may need to change settings in the File Sharing, Screen Sharing, or Remote Management pane of Sharing preferences. See Set up file sharing and Share the screen of another Mac."

If the issue continues, run a hardware test to be sure. Use Apple Diagnostics to test your Mac

If no issue are found in the diagnostic, reach out to Apple Support directly to further assist.

Contact - Official Apple Support

Contact Apple for support and service - Apple Support

Best.