The advantages of open fitting with behind-the-ear hearing aids

There are basically two types of hearing aids: in-the ear systems and behind-the-ear devices. About two thirds of hearing aids fitted in Germany, for example, are behind-the-ear systems. They consist of the device itself behind the ear and a bent tube which passes over the ear to a mould which fits in the outer ear or in the ear channel. Whereas cosmetic reasons are usually given for preferring in-the-ear devices, behind the ear hearing aids are easier to wear, easier to switch on and off, and battery changing is also less of a problem. In addition, the mould separates easily from the appliance, so that it can be cleaned regularly. And, an audio link can only be used with behind the ear system. This allows wearers to hear speech without disturbing background sound, or to connect up to sound systems.

Open fitting - advantages with sound quality and comfort

Behind the ear systems can be fitted open or closed. The latter have a fitted ear mould which more or less completely closes the outer ear and ear channel. By modifying the ear mould with drilled holes, the acoustician can alter the sound quality and the wearing comfort of the hearing aid and adapt it to the specific requirements of the wearer. Generally, the more open the mould, the more comfortable the hearing aid is to wear. An open system ensures that the ear is ventilated and helps to avoid overheating or the collection of moisture in the ear. It also helps to avoid distortion of the wearer's own voice, and the unnatural amplification of swallowing and chewing noises. (This is similar to the effect produced by talking or chewing with a finger in the ear.) The wearer experiences a more natural sound because the sound propagation to the ear drum and the directional function of the outer ear and the ear channel are maintained. Finally, there is optimal amplification in particular in the high frequency range.

Open systems – Very good but only possible with selected hearing instruments

As far as sound quality and wearer comfort are concerned, open systems are always preferable, i.e. the ear insert is always kept as open as possible. Latest developments even make it possible to do without an ear mould. The tube is inserted directly into the ear canal. However not all behind the ear appliances are suitable for an open system. The hearing aid must have an excellent quality of sound reproduction, with imperceptible noise levels and an effective suppression of feedback. On the other hand the open set could lead to unwanted amplification of signals picked up by the microphone and amplified again (feedback) causing an unpleasant high-pitched whistling sound.

An open system is not suitable for all kinds of hearing loss. It is most appropriate for cases of slight to medium loss of hearing, or for loss in the high-frequency range (precipitous hearing loss). The greater the hearing impairment, the more closed the ear mould needs to be, thus reducing the occurrence of feedback and achieving the necessary amplification.
Before choosing a suitable form of hearing aid, it is important to seek the advice of an acoustician/audiologist. Particularly for first time wearers, a thorough discussion of the options before making a choice is an important factor influencing the wearer's satisfaction with the fitted hearing system. This in turn, will help ensure that the instrument will be worn regularly and that the treatment will be successful.