I've looked everywhere online. I found out how to change the gender of the voice (synthesizer.SelectVoiceByHints(VoiceGender.Male) and the age of the voice, but I can't figure out how to change the voice's culture (aka add a british accent).
Another viable option would be to find another voice synthesizer. However, when I've tried to implement it into my program the voice synthesizer won't work.
Thank you so much for your help!
Two weeks before, I developed Speech Synthesizer tool for French and English. I followed below steps to install more voices and configured different voices by calling SelectVoiceByHints method.
You can set the culture info as below,
Steps to install more voices
You should now have access to the new voices in Voice Attack, and in the Windows TTS options menu. This process may also work with other voice packs.
Source: https://superuser.com/questions/590779/how-to-install-more-voices-to-windows-speech/872573#872573
Hope this gives some idea.