What is overspill?
Overspill is the magnetic field outside the area of the loop system. Induction loop systems are designed for hearing aid users to be present within the area of the loop. As the magnetic field will travel through walls, ceilings and floors there will always be some overspill.

This means that hearing aid users outside the looped area may be able to overhear conversations if their hearing aids are switched to 'T' position. The magnetic field of a simple one loop system will overspill into adjoining rooms and rooms directly above and below.