6 examples of acoustic filters.
<ul><li><a href="//commons.wikimedia.org/wiki/File:Acoustic_filters.png" title="File:Acoustic filters.png">Acoustic_filters.png</a>: <a href="//commons.wikimedia.org/wiki/User:Mike.lifeguard" title="User:Mike.lifeguard">Mike.lifeguard</a></li>
<li>derivative work:  <b>— <a href="//commons.wikimedia.org/wiki/User:Mike.lifeguard" title="User:Mike.lifeguard"><b style="color:#309;">Mike</b></a>.<a href="//commons.wikimedia.org/wiki/User_talk:Mike.lifeguard" title="User talk:Mike.lifeguard"><b style="color:#309;">lifeguard</b></a></b></li></ul>
<ul><li><a href="//commons.wikimedia.org/wiki/File:Acoustic_filters.png" title="File:Acoustic filters.png">Acoustic_filters.png</a></li></ul>