People who suffer from hearing loss - the unseen disability - require more than just increasing the volume of sound into their ears.
The loss of hearing is generally associated with the neurological processing of information in the brain. People with normal hearing require a signal to noise ratio of 6dB for a reasonable level of intelligibility. This represents quite a noisy background, which might be reverberation, air conditioning, ventilation systems or background noise such as a crowd of people.
When a person loses about 80% of their hearing, they generally need a signal to noise ratio of 15 to 20dB. This can be difficult to achieve unless the wanted signal is taken straight from the basic source and transmitted directly through the loop system, avoiding any reverberation or additional ambient noise.
Transient situations, such as ticket counters, information and help points, etc., are the worst areas for listening, though even in churches, theatres and lecture / conference rooms, there is often sufficient degradation of the signal to seriously affect intelligibility. In most situations it is impractical to issue any form of separate receiver and the use of the individual's hearing aid is a major step to bringing people with hearing loss back into full contact with their environment. Only induction loop systems are capable of doing this.