public Builder mergeAudioConfig(com.google.cloud.texttospeech.v1.AudioConfig value) {
      if (audioConfigBuilder_ == null) {
        if (((bitField0_ & 0x00000004) != 0)
            && audioConfig_ != null
            && audioConfig_ != com.google.cloud.texttospeech.v1.AudioConfig.getDefaultInstance()) {
          getAudioConfigBuilder().mergeFrom(value);
        } else {
          audioConfig_ = value;
        }
      } else {
        audioConfigBuilder_.mergeFrom(value);
      }
      if (audioConfig_ != null) {
        bitField0_ |= 0x00000004;
        onChanged();
      }
      return this;
    }
<pre>
Required. The configuration of the synthesized audio.
</pre>

<code>
.google.cloud.texttospeech.v1.AudioConfig audio_config = 3 [(.google.api.field_behavior) = REQUIRED];
</code>
java-texttospeech/proto-google-cloud-texttospeech-v1/src/main/java/com/google/cloud/texttospeech/v1/SynthesizeLongAudioRequest.java