MacOS has got a pretty cool background noise feature, that I like to use during focus time. You can find it under System Settings > Accessibility > Audio.
You can choose between a couple of different sounds, including Rain (which is my favourite), Ocean, Dark noise etc.
Unfortunately, this is quite a few clicks away if you want to toggle it on/off. I recently found a way to add this to the control center, which makes it much easier to use. Here is how.
Go to Settings > Control Center. Scroll down to the Hearing section and toggle Show in Control Center.
Now if you go to your Control Center, an Ear icon will show up on the bottom.
Clicking on that will bring up the background audio control.
Happy focus time! 🎧