Audio induction loop, directing the magnetic field

[bob50]

I have built a prototype audio induction loop for service counters. It is the size of an A4 sheet of paper and stands on edge on a service counter. It intentionally creates a magnetic field at audio frequencies directed towards the customer who can pick up the field via an inductive pickup on their hearing aid. I want to shield the area behind the loop to avoid interference with PC's, monitors etc. Any advice would be greatly appreciated.

 

[prex]

A thin cover made with ferromagnetic material (plain carbon steel) should be sufficient; no matter if there are a few small holes in it.
However if you go too close and around the direction where hearing is sought, the propagation of the magnetic field (and the distance for hearing) could be heavily affected : you should be able to find a compromise.
prex
motori@xcalcsREMOVE.com

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[Bootstrap]

A friend is trying to get an electromagnet to interact, solenoid style, (push and pull) with a strong rare earth magnet.
The objective is to move a iron spool. Where the coil is wound around a brass tube that spaces the inside of the coil 1/8 inch from the outside surface diameter of the moveable iron spool. The iron spool is attracted to the rare earth magnet and the electro magnet can not induce a magnetic field into the iron spool so as to free it from the rare earth magnet.
Is the 1/8 inch gap between the coil ID and iron spool OD the problem? Maybe a simular gap is needed between the spool and rare earth magnet?
Is the relative strength of the rare earth magnet is the problem?
He only gets a weak force change in the iron spool's attachment to the rare earth magnet, but the rare earth magnet does rise in temperature a bit. This happens with PWM, or DC amperage. Why? What possible error/s is/are being made?

 

[hacksaw]

in ref to the original query, at the freq's and field strengths that you'll be dealing with shielding is not required.

the steel plate would not be a good idea, as it would effectively cancel out the fields that you want to create...

now, since we are contributing to your product idea, do we get a cut...?


good luck