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Types of Hearing Aids

by on 26 May, 2013

This edition of my blog with explain  the different types and styles of hearing instruments/hearing aids, their applications and the pros and cons of each one.  First I will explain a bit about the hearing aid circuitry. Hearing aids originally had circuits that would amplify sound on a slope to try to match the hearing loss being treated. The problem with this linear (straight line) type of amplification was that, loud sounds were too loud, soft sounds were too soft and normal sounds were just right. Thus the user was forever adjusting the volume trying to achieve a comfortable level to match the volume of the surroundings that he/she was in at any given time. So the volume control was usually the first part to fail, as it was used quite a bit. Then came various loudness suppression circuits both manually and digitally controlled. These circuits were an improvement over the linear hearing aids but were still limited by an analogue (non-digital) circuit that was easily overwhelmed by the large amounts of information that needed to be processed to understand speech, particularly in the presence of background noise. This would require a new type of circuit to be developed and computerization has allowed that to happen. Over the past ten to fifteen years, there has been an integration of digital technology to control the function of shaping the sound processed by the hearing aids. This type of amplification control, allows the hearing professional the ability to program the hearing aids very finitely with the use of a computer. Now soft sounds are amplified to comfortably audible level, while loud sounds are suppressed to a loud but comfortable level and normal sounds as well as the loud and soft sounds are shaped for the best clarity possible.
Along with the digital circuitry, we have seen a switch in how hearing aids are being attached to the body. Generally speaking for a long time you either had an “In The Ear” (ITE) or a “Behind The Ear” (BTE) hearing aid.
The ITE hearing aid is made by taking a silicone impression of the outer ear and ear canal. This is shipped to the laboratory and a hard shell casting is made of the ear impression. The electronics are housed inside this casting. The size of the hearing aid is determined by the hearing professional and the client using the hearing loss and impression as a guideline to decide. Those sizes are as follows:   
CIC – a “completely in the canal” hearing aid that can barely be seen and fits the deepest in the ear canal of any style hearing aid. It is very discrete, but is limited by the degree of hearing loss and the shape of the canal of the perspective user. No controls are available on this style of hearing aid. New high power CIC hearing aids are now available, so this type of hearing aid is becoming more flexible than previously. Do to the depth of the fitting this type of hearing aid is more susceptible to moisture related break downs. 
ITC- the “in the canal” aid is slightly larger than the CIC and depending on the ear canal size can now start to accommodate both inner and outer controls, such as an external volume control or an internal remote control interface.
HS/ITE –“half shell and in the ear” aids fill either the bowl of the ear in the case of the HS or the entire outer ear cavity in the case of the ITE. These hearing aids are very common and can accommodate more internal and external controls, such as telecoils and Bluetooth interfaces.

BTE- “behind the ear” hearing aids are the most versatile hearing aids. The electronics are housed in a hard casing that is placed on top of and behind the ear, hooking where the top of the ear meets the cheek bone. The aid is then coupled to an ear mold via silicone tubing or plastic thin tube. Sound travels from the BTE through the tube into the ear mold and into the ear canal. The ear molds can be custom made in the same sizes as the ITE hearing aids, as well as pre-molded silicone molds for instant in office fittings. BTE hearing aids come in a variety of sizes and colours. These aids can accommodate the widest variety of ear canal sizes as well as the different degrees of hearing loss from mild to profound.
Hybrids- these are the newest aids and can be ITE’s with a remote microphone or a BTE with an in the canal receiver/speaker system. This last hearing aid style is known as; a “RIC” (receiver in the canal), a “CRT” (canal receiver technology” or a “RITE” (receiver in the ear). They all have the hearing aid housed in a casing like a BTE and a speaker system attached via a plastic coated wire. These hearing aids are widely used because of their comfort and flexibility for fitting a wide variety of hearing losses and ear shapes very effectively.
These are the main hearing aid styles and types. If you have any questions about whether a style or type of hearing aid is right for you contact  A & E Hearing Care and book a hearing evaluation and consultation.


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