Hearing Loop System - Key Requirements

Hearing Loop System - Key Requirements

1. Increases signal to noise ratio

The system must greatly improve upon the signal to noise ratio that can be achieved with a standard hearing aid or cochlear implant that is not connected to a hearing loop.

Examine the input source(s) and select an amplifier and adaptors to suite.
  • If using microphone(s) as an audio source - microphone type and placement is crucial;
  • Do not use omnidirectional microphones (especially in ceiling tiles) for area coverage applications, as it will generally only achieve as good an effect as the microphone in the user’s hearing aid, if not worse.
2. Provides suitable area coverage for the application

Determine what the use, or uses, of the space in which a proposed installation will be.
  • If the space contains fixed seating the listening height will be approximately 1.2 meters, the systems loop design and amplifier power requirement must accommodate this;
  • If the people using the loop system are free to stand and move around in the space then the listening height will be approximately 1.6 meters. This scenario also precludes the use of Simple Single Phase Array loop designs (figure of 8 etc) which leave ‘dead spots’;
  • If the area contains a staged entertainment area where microphones and electrical instruments will be used then a Cancellation Loop or Low Spill Multi Loop Phased Array loop design is required to prevent the signal interacting with on-stage equipment;
  • As much of the available space as possible should always be looped. Providing a small looped area for hearing aid users is not acceptable as this is likely to separate users from their friends and family, which is discriminatory.
3. Is not susceptible to interference from background noise

Electromagnetic Noise can be created by faulty wiring and local substations. It can affect intelligibility and provide an uncomfortable listening experience.
  • Check how much electromagnetic noise is experienced in the looped area using a suitable meter. Must be less than or equal to -32dB (A-weighted);
  • Where possible, noise should be addressed at its source, such as fixing faulty wiring or ground loops.
4. Generates the correct field strength

A Hearing Loop system functions by producing an alternating magnetic field at audio frequencies which provides an input signal for hearing aids operating with a telecoil. If the field strength is too low then intelligibility and signal to noise ratio are compromised, if the field strength is too high then the hearing aid may be overloaded.
  • Field strength at the listening plane (ear height) should be 400mA/m sine wave @ kHz and checked using a suitable meter.
5. Provides an even field strength

A Hearing Loop system should provide a constant field strength throughout the listing area so the signal doesn’t vary greatly as the users of the system move around.
  • Field strength must remain within a tolerance of ± 3dB over the entire listening area.
6. Provides a flat frequency response

Hearing Loop systems can be used to transmit music, the human voice or generally both. Human speech produces specific frequencies to form words. It is essential that the system is capable of replicating these frequencies to maintain the intelligibility of the audio broadcast to the users of the system.
  • Frequency response of 100Hz – 5kHz ± 3dB ref. level @ 1kHz Must be maintained across coverage area;
  • Ensure that the specified amplifier is capable of generating sufficient power and voltage headroom;
  • Maintain the correct field strength.
7. Displays clear signage, no user request necessary

Induction loops are designed to be invisible. Nobody will use the system if they don't know it is there. Hearing Loops are popular with users because they are a dignified solution that doesn’t require them to identify themselves, if they have to ask if a Hearing Loop is present this advantage is lost.
  • Signage should be provided at each entry point to the looped space and at least one clearly visible sign should be within it.
8. Can be operated and maintained by venue staff

When installing a Hearing Loop it is not enough to simply make sure that it is working. Staff at the venue must be trained to use systems and help customers. Although a Loop system should be a fit-and-forget feature they are susceptible to ‘janitorial adjustments’ by untrained parties, mainly because they don’t produce an audible signal. They must therefore be regularly checked.
  • A Loop Receiver with basic field strength indication must be provided with each loop system and staff must be shown how to use it, how often to check the system and how to make basic fixes.

ApplicationHearing Loop Amplifier TypeLoop Type
Meeting room or 1:1 communication requirement in busy or noisy  environmentsPortable table top loop systemOn-board device
Retail Point-of-SaleFixed counter loop amplifierPreformed Multi-turn Overspill Loop
Customer Service or Reception DeskFixed counter loop amplifierPreformed Multi-turn Overspill Loop
Bank teller or security windowFixed counter loop amplifier & line-ln from duplex intercom systemPreformed Multi-turn Overspill Loop
Room with shortest aspect of less than 4 metersSingle output phase amplifier*Perimeter Loop
Room with shortest aspect of less than 15 meters in a building with no  structural metalSingle output phase amplifier*Perimeter Loop
Room with shortest aspect of less than 15 meters in a building with no  structural metal & a stage area for electrical instruments.Single output phase amplifier*Cancellation Loop
Room with fixed seating and shortest aspect of less than 15 meters, in a  building with modern structural metal constructionSingle output phase amplifier*Simple Single Phase Array (Figure 8 etc.)
Room with shortest aspect of greater than 4 meters, in a building with  modern structural metal constructionDual output phase amplifier, or 2 amplifiers with master/slave  configuration and a 90°phase shifter*Low loss Multi Loop Phased Array
Boardroom with shortest aspect of greater than 4 meters, in a building  with modern structural metal constructionDual output phase amplifier, or 2 amplifiers with master/slave  configuration and a 90°phase shifter* & line-in from conferencing systemLow loss Multi Loop Phased Array
Room with shortest aspect of greater than 4 meters, in a building with  modern structural metal and a stage area for electrical instrumentsDual output phase amplifier, or 2 amplifiers with master/slave  configuration and a 90°phase shifter*Low Spill Low loss Multi Loop Phased Array
Room with shortest aspect of greater than 4 meters, in a building with  modern structural metal and a other Hearing Loops system close by (vertically  or horizontally)Dual output phase amplifier, or 2 amplifiers with master/slave  configuration and a 90°phase shifter*Low Spill Low loss Multi Loop Phased Array
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