What happened to porridges voice?

You're likely thinking of Porridge, the popular British sitcom starring Ronnie Barker. In the show, Ronnie Barker's character, Norman Stanley Fletcher, has a distinctively high-pitched voice.

This wasn't just an acting choice. Ronnie Barker had a naturally high-pitched voice, which he often used to comedic effect.

There was no specific incident or event that changed his voice; it was simply his natural vocal range.

However, some people might say that his voice changed slightly over time, possibly due to aging or the demands of his acting career.