how do i change siri to a female voice

I seem to recall that Siri's voice characteristics are determined by either your geographic location or the Language settings for it in the Settings app (not sure which). But basically it is not configurable in terms of allowing you to select a specific voice.

Siri's voice depends on your location. UK is male, whilst US and Australia is female. You can change it using these instructions. Changing your location may result in issues with recognition and dictation, as the languages are slightly different.

You can change Siri's voice via settings, follow the steps listed below for help:

Go to Settings>General>Siri> Scroll down and you can change the voice gender and voice language. There are even diffrent choices of english like,

(ex: English United Kingdom styled ) or (English Canada styled.)

You are responding to a question that is over two years old and Siri became configurable since the OP posted the question.