I had a microphone logo instead of Audacity headphones, but (a) it did not work so well in small sizes and (b) it lost some of the connection with Audacity, so I re-instated a more Audacity like headphones logo.   The microphone can still be seen on the splash screen of the installer.  I decided not to give the logo a white surround.  The result is that on a dark windows toolbar it can almost disappear into the background, but becomes visible when you hover.