如何使用ssml韵律元素产生情感语音？

Question

如何使用ssml韵律元素来产生情感语音？

我已经尝试过使用这段代码在语音中产生悲伤的情绪，但是语音情绪没有变化。

static void Main(string[] args)
{
    SpeechSynthesizer synth = new SpeechSynthesizer();
    PromptBuilder pb1 = new PromptBuilder();

    string sad = "<prosody  pitch=\"-20%\" range=\"low\" rate =\"50%\" volume =\"30\"><emphasis level=\"none\">... She  was  sad.  Ellen  cried.  Calvin  said, I  feel  guilty.  Calvin told  Daddy Sam that he broke the lamp.</emphasis></prosody>";

    pb1.AppendSsmlMarkup(sad);
    synth.Speak(pb1);        
}