@java.lang.Override
  public void writeTo(com.google.protobuf.CodedOutputStream output) throws java.io.IOException {
    if (((bitField0_ & 0x00000001) != 0)) {
      output.writeMessage(1, getVoice());
    }
    if (((bitField0_ & 0x00000002) != 0)) {
      output.writeMessage(4, getStreamingAudioConfig());
    }
    getUnknownFields().writeTo(output);
  }
<pre>
Optional. The configuration of the synthesized audio.
</pre>

<code>
.google.cloud.texttospeech.v1beta1.StreamingAudioConfig streaming_audio_config = 4 [(.google.api.field_behavior) = OPTIONAL];
</code>
java-texttospeech/proto-google-cloud-texttospeech-v1beta1/src/main/java/com/google/cloud/texttospeech/v1beta1/StreamingSynthesizeConfig.java