There are two main ways to disable the lights.

1. Use an App that can continuously play the OFF frequency in the background.
   Tone generator is one such Application. 

2. If the new App you are running in the foreground cuts out background audio when opened. Then the only option you have left is to physically unplug the LED lights from the electronic housing at the back of the enclosure.
   This can typically be done without removing the tablet from the enclosure. Simply remove the M3 screws holding the enclosure to the wall mount. Now that you have access to the back of the unit you can unplug all the LED lights going into the electronic housing. Then reinstall the enclosure back onto the wall mount.