A wavefile in a waveeditor, its envelope marked with a thick red line.
<a href="//commons.wikimedia.org/wiki/User:Gladiool" title="User:Gladiool">Gladiool</a> - Uploader of the original was <a href="https://en.wikipedia.org/wiki/User:Scoofy" class="extiw" title="en:User:Scoofy">Scoofy</a> at <a class="external text" href="https://en.wikipedia.org">en.wikipedia</a>
PNG version of <a href="//commons.wikimedia.org/wiki/File:C_Envelope_follower.jpg" title="File:C Envelope follower.jpg">File:C Envelope follower.jpg</a>