showSpeechAtPosition(position, text, sound, duration, isNotDismissable) {
    let showDuration = 0.0;
    const speechNode = SpeechNode.create();
    speechNode.setPosition(position);
    this.uiLayer.addChild(speechNode, this._ui_z_order_speech_nodes);
    showDuration = speechNode.showTextWithSoundForDuration(text, sound, duration, true, isNotDismissable);
    return showDuration;
  }
Shows a speech node over a tile in the game
@param {object} position - object with x and y properties representing tile indices
@param {string} text - string of text to show
@param {string} sound - resource string for sound to player
@param {number} duration - how long to show the speech node
@param {Boolean} isNotDismissable - whether speech is not dismissable
@returns {SpeechNode} - SpeechNode being added to screen