Try overwriting the executable in Map Monkey\Plugins\ExternalAudio with this
I use Mapmonkey and use the sound card plugin to have the voice prompts output to the second sound card, so it is using the SDK to make all those voice prompts.
Since then, all the prompts are given in yards instead of Kilometers. Is there anyway to change it? Also, one wired thing is that the first notification should be 3KM before a turn. It does do it, but instead of saying 3KM (or yards equivalent) it say it is only 500 yards, which suppose to be the second nitification voice prompt.
Maybe Ninja Monkey can shed some light on this?