How can I put my Mac to sleep when the lid is closed while attached to a monitor?

Hello, I recently set up my workspace so I am using an external monitor. Now, my MacBook won't go to sleep.

When I close the lid, all the windows go to the monitor. When I select "Sleep" from the Apple menu, the screen turns off but I am still getting notification sounds and dings. I have "Wake for network access" turned off.

Any other ideas? So far the only way I have been able to solve it is by muting my computer and removing the HDMI cord at night, which is a pain.