code: protected Attachment getAudioMessage(MessageEnvelope envelope) {
  		if (envelope != null
  				&& envelope.getMessage() != null
  				&& envelope.getMessage().getAttachments() != null
  				&& envelope.getMessage().getAttachments().get(0) != null
  				&& envelope.getMessage().getAttachments().get(0).getType() == AttachmentType.AUDIO) {
  			
  		
  			return envelope.getMessage().getAttachments().get(0);
  		}
  		return null;
  	}
docs: Gets the audio message.
  
  @param envelope the envelope
  @return the audio message