web-audio-peak-meter/examples/nodom.html

A customizable peak meter using the web audio API

<p>
  The web audio API context is <span id="ctx-status">loading</span>.
  <button id="ctx-button">Loading</button>
</p>

<audio id="the-audio" preload="metadata" crossorigin="anonymous" controls="controls">
  <source src="https://assets.rpy.xyz/testmedia/semper_fidelis.mp3" type="audio/mpeg" />
</audio>
<div>
  <button id="clear-peaks">Clear Peaks</button>
  <button id="get-peaks">Get Peaks</button>
</div>
<ul>
  <li>Current peaks (floating point): <span id="current-float"></span></li>
  <li>Current peaks (decibels): <span id="current-db"></span></li>
  <li>Channel maxes (floating point): <span id="maxes-float"></span></li>
  <li>Channel maxes (decibels): <span id="maxes-db"></span></li>
</ul>