private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.texttospeech.v1beta1.StreamingAudioConfig,
            com.google.cloud.texttospeech.v1beta1.StreamingAudioConfig.Builder,
            com.google.cloud.texttospeech.v1beta1.StreamingAudioConfigOrBuilder>
        getStreamingAudioConfigFieldBuilder() {
      if (streamingAudioConfigBuilder_ == null) {
        streamingAudioConfigBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.texttospeech.v1beta1.StreamingAudioConfig,
                com.google.cloud.texttospeech.v1beta1.StreamingAudioConfig.Builder,
                com.google.cloud.texttospeech.v1beta1.StreamingAudioConfigOrBuilder>(
                getStreamingAudioConfig(), getParentForChildren(), isClean());
        streamingAudioConfig_ = null;
      }
      return streamingAudioConfigBuilder_;
    }
<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