Without notice, we just spotted the default html5 player has recently added a new feature as to set "Playback speed".
This is the screenshot of a random page that host default html5 audio player(using <audio>tag in html). When you click the three point at the right edge of the player, you could see the pop-up menu of "Playback speed".
You would find the speed could be as fast as double speed, as well as slow as a quarter speed.
This is the feature that we always wanted to add to website and now it came automatically to default html5 players. It is extremely useful when we learn a new language.
If you could not find this new feature, you might want to upgrade your browser to the latest version or use Google Chrome or Microsoft Edge.