Both technological advances and the increasing attention to aesthetic factors have lead to the development of many different solutions.
Main types of hearing aids
The first criterion to be considered in classifying hearing aids is their position in relation to the ear while another criterion is the type of technology used for the reproduction and amplification of sounds.
The position of the hearing aid is important also from an aesthetic point of view. In general, hearing systems can be divided into four main groups:
- Behind the ear: positioned behind the ear, the aids transmit sounds to the eardrum by means of a small tube linked to a made-to-measure earpiece which is inserted inside the auditory canal. They are easy to regulate, even by patients themselves, and allow the correction of very severe hearing loss.
- In the ear: placed inside the auditory canal, these aids are not easily seen and for this reason they effectively combine the correction of hearing difficulties with the aesthetic requirements of patients. However, a higher level of maintenance and cleaning is required, precisely because of their position.
- Glasses: a comfortable solution which is not easily seen because the circuits are inserted in the arms of a pair of glasses; depending on the method of transmitting sound to the ear, these can be divided into aids with aerial conduction (amplified sounds reach the eardrum via an earpiece inserted in the auditory canal) or aids with bone conduction (the aid transforms sounds into vibrations which are then transmitted to the mastoid bone).
- Box: these aids are only used for very severe hearing problems which necessitate a very high level of amplification. They consist of a box containing all the electronic circuits and a connecting wire which transmits sounds to an earpiece.
The technology used determines the way in which sound signals are processed and also the options for adapting the hearing aids to the individual's needs. There are three options.
- Analogue: sounds are processed analogically and the characteristics of the hearing aids are selected using potentiometers which are adjusted by the hearing-aid specialist. This is a robust system and it is possible to obtain very clear output signals which means it can be used to correct even very severe hearing problems. Even so, this type of aid is sensitive to changes in temperature and humidity and has limited programming options.
- Programmable: the aids are programmed and adjusted via a computer which allows considerable precision and flexibility; it is possible to memorise different settings which can be used in the different situations which the patient expects to be in.
- Digital: these are obviously the most developed aids both in terms of the sound quality and the possibilities for adjusting the aids; incoming sounds are processed and cleaned by the process of digitalisation which gets rid of the background noise. In addition, the reduced size of the circuitry permits better performance and better adaptation.
