Sound from road signs?

Audio files have nothing to do with TTS. Only a properly configured sys is required
[Only registered and activated users can see links. ]

When you use adapted TTS lang & voice files, the TTS engine is responsible for all that. It is also possible that you have adjusted the skin incorrectly, you are using inadequate files, etc... maybe you didn't set up your phone/system properly.
Read announcement: [Only registered and activated users can see links. ]
and respond.

And read the all TTS/voice relevant topics