初始化 SpeechSynthesizer 时出现 UnauthorizedAccessException

我正在使用 Microsoft 的 SpeechSynthesizer 为我的 Windows Phone 应用程序创建音频输出。我用这个代码

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();

确保您已添加该功能ID_CAP_SPEECH_RECOGNITION到应用程序清单 (WMAppManifest.xml)。