Mysterious notifications within OS

[Lourdan]

I am running Mac OS High Sierra which I've used since it was released without any problems. I use it because it is the last OS that I can use my PS CS6. Anyway, I am now getting notices appearing right under the toolbar accompanying by a whistling sound. The notice only lasts for 2 or 3 seconds but it can open windows, apps etc without my activation. It happen mostly when using YouTube but can also happen with safari and effects not only my iMac but my iPad, iPhone but the notices only appear on my iMac. I've tried disabling Automator but to no avail. When I activate screen shot (shift/Command/4) it seems to inhibit this problem but I'm not sure.
Examples of the notices: Launch (a window opens), Open Automator, Open Notes, Open Apps, Go to the beginning, Cut that, Delete this, undo that, open grab, redo that, click Apple Support, Delete selection, find this..., Show preview, Search: Teeth, Open font book, Seri, etc.

I am not a geek so I am at a loss as to what is causing this problem with is annoying.

Any suggestions would be appreciated.

 

[Cory Cooper]

Hello and welcome.

Sounds like you are seeing Notifications banners or alerts, or you have some errant browser extension installed. Not sure why they would list those activities, as they are Finder functions.

If you could attach a screenshot of one of the alerts, that may help us diagnose the issue.

Let us know what is listed in the following:
 > System Preferences.. > Users & Groups > your user > Login Items
Safari > Preferences... > Extensions

You could try enabling Do Not Disturb in Notification Center to prevent the alerts:
Use Notification Center on Mac

Let us know if that helps,

C