Anechoic tile scheme, based on <a href="//commons.wikimedia.org/wiki/File:UBOAT1308_5.png" title="File:UBOAT1308 5.png">File:UBOAT1308 5.png</a>.
<a href="//commons.wikimedia.org/wiki/User:Pko" title="User:Pko">Pko</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>