What is this icon with a square and a waveform in Apple Watch Control Center?

I noticed this icon in Control Center on my Apple Watch recently and didn’t recognize it. It’s not listed on Apple’s support pages about Control Center (a b). UPDATE: This page now includes this icon.

Screenshot of Control Center on Apple Watch

(bottom left)


Solution 1:

I was able to determine the button’s purpose through VoiceOver, which reads this button as “announce messages”.