code: function SoundManager(manifest) {
    /**
     * A flag signifying if sounds have been muted through {@link SoundManager#mute}.
     * @member {boolean}
     * @private
     */
    this.muted = false;
    /**
     * A key-value object that stores named looping sounds.
     * @member {object}
     * @private
     */
    this.looping = {};
  
    /**
     * The Web Audio API AudioContext
     * @member {external:AudioContext}
     * @private
     */
    this.context = new window.AudioContext();
  
    this.gainNode = this.context.createGain();
    this.gainNode.connect(this.context.destination);
    this.volume = this.gainNode.gain.value;
    this.installSafariWorkaround();
    this.assets = new AssetLoader(manifest, loadSound.bind(undefined, this.context));
  }
docs: Plays audio, tracks looping sounds, and manages volume.
  This implementation uses the Web Audio API.
  @constructor
  @param {Object} manifest A hash where the key is the name of a sound, and the value is the URL of a sound file.