Vance Muff Headphones were designed by Jeremy Vance of Vance Metal Detecting.  In the quest for having a wireless headphone that actually blocked ambient noise but also had a very good speaker! 

We tested 27 speakers at 13 different ohmages for a total of hundreds of speakers before we finally chose one to install..  These headphones have reviewed very well in comparison to all the others...  see link below..

http://www.detecting.us/2014/06/03/headphones-for-xp-deus-comparing-gray-ghost-and-vances-headphones/