Unknown notification on my MacBook Air

That water drop notification sound on your MacBook Air could be coming from a few different sources, especially if it happens intermittently and doesn’t correspond to any visible notification or alert on screen.

See if any of the following can help you track it down:

• Go to System Settings > Notifications. Review the apps that have permission to send notifications and their alert styles. Some apps might have sound alerts without banners being enabled.
• Some third-party apps running in the background (like messaging apps, cloud storage services, or even calendar reminders) could be the source of this sound. Open Activity Monitor (in the Utilities folder within Applications) to see what's running and try quitting any apps that might be the culprit.
• Enable Focus Mode to see if it stops the sound. This can help you determine if a notification or an app is causing the noise. If the sound stops while Focus is active, you can tweak your Focus settings to block specific apps or notifications.
• System notifications like disconnecting peripherals or Wi-Fi changes could play a sound. Go to System Settings > Sound, and under Sound Effects, try disabling "Play sound effects through" or set the alert volume to zero.