Restoring email and Siri voice after iOS 18.2.1 update

If you have updated to include Apple Intelligence, the new Siri voice (which I quite like better, to be honest) is the new normal, and you cannot go backwards.

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H8updates wrote:

How do i put my email and Siri’s voice back to normal after update 18.2.1?

[Re-Titled by Moderator]

What does back to normal mean?