Metal structures

Metal in buildings – the impact on hearing loops

Metal in buildings – the impact on hearing loops cannot be underestimated. The importance of designing hearing loop systems to cope with losses, caused by metal structures within the fabric of buildings, is significant. It is absolutely critical to allow for signal loss caused by metal structures during the system planning phase of any installation. If this is not done, the installed loop system is likely to suffer from a range of problems – insufficient signal strength, uneven signal strength – loud in places and inaudible in others, lack of high frequency detail / clarity or other problems. Metal loss problems can be overcome but only by proper design and attention to detail.

The Ampetronic Support team can help you to assess and compensate for the metal structures in your application. For more information on hearing loop design to meet regulatory Standards for hearing loop installations, contact our friendly and knowledgeable team on +44 (0) 1636 610062

Using the HLS-2D Metal Loss Test Kit, to deliver a preset output level to give consistent test results,  combined with the Loopworks Measure R1 or Ampetronic FSMprovides an ideal aid to quick and simple site assessments.

See HLS-2D Metal Loss Test Driver


The magnetic field generated by an induction loop system, induces a current in any closed path of a metal structure placed in the vicinity of the induction loop. Further Information.

These induced currents tend to weaken the magnetic field and cause loss. This loss is dependant on the type and thickness of metal and its position in relation to the induction loop.

Examples of Metal Structures

  • Reinforced concrete floors – often containing a mesh. Further information about reinforcing meshes
  • Lightweight floor construction with a (usually profiled) metal sheet under a thin reinforced concrete slab
  • Metal floor tiles – System floors
  • Suspended ceiling grid – 600mm x 600mm (2′ x 2′) or 1200mm x 600mm (4′ x 2′) metal grids with acoustic or metal tiles
  • Foil backed plasterboard – Vapour barrier
  • Girders, beams, constructional metalwork
  • Metal cladding, walls and roofs
  • Metal counters – Whole or part metal
  • Metal box construction – Elevators / lifts

Metal Loss Demonstration Video

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