How to add new sound using

I create a class ------

class Bgm extends Phaser.Sound {
  constructor({ game, key, volume, loop }) {
    super(game, key, volume, loop);


and I new it in a state with ------ = new Bgm({ game: GAME, key: "bgm", volume: 0.5, loop: true });

instead of ------ ="bgm", 0.5, true);

however, I cannot add it to game just like image or sprite using ------; // in my class

how can I add audio using such ES6 style?