I've never seen that, in vanilla nor in ZRP games -- if you have the psy_helmet. Are you playing through X16 without one? Still, shutting down the brain machine should stop the effects.
You are also known for extensively modifying your game. There might be something you've changed that keeps the info_portion yantar_attack_start from being given or processed correctly when you shut off the main switch. This stops the sounds and other effects.
As a test, you could give yourself that info_portion in a save that still has the voices/effects after you have shut down the Miracle Machine. If it stops the effects, then you could trace where it was supposed to be processed when you flipped the main switch.