初始化 SpeechSynthesizer 时的 UnauthorizedAccessException

我正在使用Microsoft的SpeechSynthesizer为我的Windows Phone应用程序创建音频输出。我使用此代码

private async void TextToSpeech_Tap(object sender, System.Windows.Input.GestureEventArgs e)
{
    SpeechSynthesizer synth = new SpeechSynthesizer();
    await synth.SpeakTextAsync("You have a meeting with Peter in 15 minutes.");
}

我得到这个异常：

{System.UnauthorizedAccessException: Access is denied.
at Windows.Phone.Speech.Synthesis.SpeechSynthesizer..ctor()
at NerdQuiz.Question.<TextToSpeech_Tap>d__1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>b__0(Object state)}

我发现错误发生在

new SpeechSynthesizer();