Speech is one of the flashiest accessibility features. It’s something that can be helpful to a lot of people while making them feel like they live in a futuristic world where computers can talk to you.
You can find Speech settings by going to System Preferences > Accessibility > Speech

System Preferences > Accessibility > Speech
System Voice Options
You can choose from a variety of system voices via the drop down menu. Alex is the default. You also have Fred, Samantha, and Victoria. Fred and Victoria are classic mac voices and sound like it too. Meanwhile, Alex and Samantha are much smoother voices based off American English Accents.
The last option on this dropdown is customize. This brings up a lot more voice options to choose from. Select the ones that sound good and try them out. This option also shows different language options.
Speaking Rate
Speaking rate is is on a scale from slow to fast. Normal speaking rate is right in the dead center. Adjust this and hit the play button to sample the voice and rate together.
Now that you have your voice and rate set to where you think you like it, go ahead and highlight a chunk of text, right click, and choose speech > start speaking.

Enable Announcements
When you check this box it will speak to you every time there is a notification or if an application needs your attention. There is an option button that becomes available after you check the box allowing you to choose voice, phrase, and delay.
Phrase options include speaking which application needs your attention or a selection from the phrase list including excuse me or alert. You can also edit the phrase list if you were looking for a different alert such as “AMELIA! I NEED YOUR ATTENTION!”
Delay is how many seconds does it wait after the alert has appeared on the screen to speak it.
Click the play button to sample what that sounds like.
Speak Selected Text When Key is Pressed
Let’s you choose a key combination that will speak selected text when pressed so you don’t have to right click. Just another option.
