APPLE INSIDER
Whether it’s because you don’t like Apple’s default choice of Siri voice, or because you simply want a change, you can change Siri’s language, accent, and gender. Here’s how to do it.

Siri’s voice has been improved over the years, but she chiefly still sounds like the same woman she always did — if you’re in the US. If you’re in the UK instead, for instance, Siri sounds like he always did.
Source: APPLE INSIDER