Mysterious hourly voice on iMac

Ok, you are good there. The next step is to check for a script running in one of the 3 launch folders. There are a couple of approaches you can take to find it.

• The easiest one and done method is to post the free EtreCheck report that will list the processes that run in all of the launch folders. The report contains no personal information and you post it here using the Additional Text option when posting.

How to use the Add Text Feature When Post… - Apple Community

• The other way is to post what you have in the most common folder where you would see it, and if not there we can check the other 2. Go to the Finder and choose the Go menu, then Go to Folder. Enter ~/Library/LaunchAgents. Don't forget the "~" character and post the screen shot here.

• Announce the time: If you turn on this option, click the Interval pop-up menu, then choose when to announce the time (on the hour, on the half hour, or on the quarter hour).

Change the menu bar clock format on Mac - Apple Support

Check for a Shortcut in the Shortcuts app. It is the latest Social Media craze to install a shortcut that will play an audio file under certain conditions or voice dictation of phrases. After you launch Shortcuts, click the All Shortcuts tab in the sidebar. You may be able to identify it by name or run it to see if the voice plays.

Is it a Computer-Generated Voice or a real voice? And what quote? Could it be the Live Speech samples?

Do you have this set?

System Settings > Control Center > Clock > [ Clock Options… ] > Announce the Time > Interval > On the hour