To hear speech output you require a speech engine to be installed on your device[phone, in car unit etc]

As i have previously stated i use the Android default engine-Google TTS output engine.

You have to download your choice of language and gender. You can also set the voice pitch and rate.

This then is what you will hear on your output device.

The file that you enter into "content/voice" is only the book that the speech engine reads from.

So you see, what you hear is the google TTS voice reading from your selected text input.

The name that the voice says is written into the info file within the voice file, and if you have Serena written and choose a male voice you will get Serena speaking as a man.