Loop Performance Standard IEC 60118-4:2006

The variation of field strength across the listening plane must not change by more than +/- 3dB

This means that the system should be usable throughout the looped area without the need for any adjustment to the hearing aid. With a poorly designed system, the signal level can change very rapidly with the slightest movement.In this situation you would need to continually adjust the volume control of your hearing aid as you moved round the room.If you have ever seen a hearing aid user standing at a ticket counter fiddling with their hearing aid and constantly adjusting their position, it is probably because the magnetic field is too variable.

It can be technically challenging to control the field strength over a useable volume of space at a counter and as such the standard is relaxed for counter loop systems allowing a total variation of field strength in the listening volume of 9dB.Unfortunately, the standard does not define the useable listening volume.So all counter loop systems that comply with the standard are not equal.

The Frequency Response of the system must be within +/-3db of the level at 1KHz from 100Hz to 5kHz

This parameter is designed to maintain the intelligibility of the signal.If the higher frequency sounds arereduced, the sound is muffled and speech is more difficult to decipher.

Without good experience, you can not use a loop listener to check the frequency response simply by listening.Your hearing will compensate for the poor quality of the signal.Just because it sounds OK for you, it does not mean it is good enough for the hard of hearing.

Maintaining a uniform frequency response is challenging requiring more powerful amplifiers.

The Background Magnetic Noise over the listening volume should be no worse than -47dB(A). However, a background magnetic noise level no worse than -32dB(A) is acceptable.

If the magnetic noise is between -22dB and -32dB, further investigation into the nature of the noise is required before an induction loop system can be installed. The background noise may sit outside of the frequency response of the hearing aid and therefore presents no problem. Or possibly, the background noise is due to an electrical fault, which, in any event, must be rectified.

Good Signage

There is no sense in installing a loop system if no one knows about it.You need to advertise its presence.If the whole area is not covered by the loop, a coverage map should also be clearly displayed.

The international sign depicting the presence of an induction loop is

It is often displayed alongside text …

' To use the Induction loop systems switch your hearing aid to the T- position '

Staff Training

Customer facing staff should Know:

• What an induction loop sysytem is
• Which areas in the facility are covered by an induction loop system
• How to switch the induction loop system on
• How to check that the induction loop system(s) are working
• What to do if the induction loop system is not working
• They should be 'deaf aware'

Maintenance

Good quality, professionally designed and installed induction loop systems rarely break down but all too often they do not work well or work at all. This is because, they get turned off, the microphones are moved, covered or unplugged, the controls on the amplifier are adjusted or the loop is cut or disconnected. Since no one apart from the hearing aid user listens to the system, no one knows. It is therefore important that a routine test and maintenance programme is in place. We recommend that the Hearing loop systems are:

• Checked by staff using a loop receiver monthly and before any event.
• Inspected for mechanical and electrical issues, and tested using a Field Strength Meter using the IEC60118-4:2006 standard as reference