The 8 key requirements for a functioning loop system can be covered by the following points.
1. Input audio to separate signal from noise
The signal on the loop should improve on the signal picked up by the hearing aid microphone
2. Acceptable coverage
Determine room use & seating layout Will the listening audience be seated or standing?
3. Low background noise
Electromagnetic Noise should not affect intelligibility = -32dB or better (A-weighted)
4. The correct field strength
Strength = 400mA/m sine wave @ 1kHz so as not to overload hearing aids or increase signal to noise ratio
5. Even field strength
Strength ± 3dB over the listening area. Signal should not vary as the hearing aid user moves around the looped area.
6. Flat frequency response
100Hz – 5kHz ± 3dB ref. level @ 1kHz Must be maintained across coverage area. Essential to maintain intelligibility and replicating human speech.
7. 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
8. Training, monitoring & maintenance
Staff must be trained to use systems and help customers. Loop systems must be regularly monitored.