This is a great new plugin by Zarko Kaktus that allows you to analyse sound frequency data. It extends the native Phaser.Sound object and provides a real-time data analyzer.
In the background the object uses a Web Audio AnalyserNode. This node is attached to the main Phaser main sound context. If the browser doesn't support Web Audio API then you can set this object to provide fake data and still have the visualization effects.
Example code is provided in the git repository, along with instructions on getting started. This is a great way to add audio interactivity to your games and sites.