Hi there,
My name is Bogdan and I'm from Romania.
I'm a mechanical engineer specialized in the industrial robotic field, 3D designer and modeler.
I can design the safety feature you wanted, with the possibility to adjust the upper limit where the headphones switching off, and also could have a lower limit - to turn on.
In this way, I invite you to open a msg channel here, and we'll discuss all the details of your project.
Regards
Bogdan