Movie Maker 3D supports a little-known (and slightly geeky) feature called Speech Synthesis Markup Language (SSML).
SSML is an open internet standard supported by Apple, Google and Movie Maker 3D that enables you to change speech rate, voice name and emphasis right in the voice animation text.
For example, you can slow the voice of an avatar by adding SSML markup to your text. Here is an example of how to use it to slow the speech:
<prosody rate=’slow’> Hello, my name is John.</prosody>
Here is an example of adding a 1 second delay between two sentences:
How are you today? <break time=’1s’/> I am fine.
You can go to the SSML spec for more information on the various markup options that are available: https://www.w3.org/TR/speech-synthesis/#S3.2.4
Not all of the SSML options are available because Movie Maker 3D uses Apple’s Speech Sythesizer and it doesn’t support all of them.