public Builder setAudioTopic(java.lang.String value) {
      if (value == null) {
        throw new NullPointerException();
      }
      audioTopic_ = value;
      bitField0_ |= 0x00000100;
      onChanged();
      return this;
    }
<pre>
Description of the content. Eg. "Recordings of federal supreme court
hearings from 2012".
</pre>

<code>string audio_topic = 10;</code>

@param value The audioTopic to set.
@return This builder for chaining.
java-speech/proto-google-cloud-speech-v1p1beta1/src/main/java/com/google/cloud/speech/v1p1beta1/RecognitionMetadata.java