A hearing aid works on the principle of amplifying the surrounding sounds to make it louder and clearer, so that it can be used to enhance your existing hearing. Hearing aid is suitable for people who have some level of hearing. Hearing aid very rarely restores hearing to normal.
Hearing aids available now days are a great improvement on the ones which were available couple of decades ago. The sections below describes various kind of hearing aids available in the market today.
Analogue or digital hearing aids
In Analogue aids, microphones help process the sound (amplify) as an electrical signal. Sound is amplified at the same level uniformly, for example, in hearing the music from the speaker, both the surrounding noise and the sound from speaker will be amplified. The final amplified sound will produce the same distortion picked up from the surroundings.
The digital hearing aid converts the audible sound (sound waves) into binary codes (digits- 0, 1), amplifying them louder and clearer, and then reconverting them back to audible sound for the listener. This helps personalise the aid as per the individual’s requirement’s and comforts.
Since the sound is digitalized, it can be manipulated to filter out all unwanted noises. Most of the digital aids are programmable with different level of settings, for example a crowded place like a concert or a quite library.
Digital hearing aids used to be very expensive, but with advancement in technology, they are getting cheaper and nowadays cost in the same range as analogue hearing aids.
Behind the ear (BTE) hearing aids
Behind the ear aid have an earmould that adjusts adequately inside the ear and the remaining part of the aid rests hidden behind the ear. Models with two microphones help to switch between comprehensive ranging to more specific or directional ranging which can help focus on what you want to hear in a noisy environment.
Aids with “open ear fitting” contain a soft earpiece at the end of the tube (instead of an earmould). This type of hearing is difficult to spot than earmould and gives very natural sound, but only advisable for people who suffer from mild to moderate hearing loss.
Receiver in the ear (RITE) hearing aids
The "receiver in the ear" (RITE) hearing aid is a newer development which is suitable for people suffering from mild to severe hearing loss.
The receiver (loudspeaker) of the RITE is positioned in the ear-tip instead of the separate housing to reduce its size. RITE hearing aid is made up of 3 components: The housing, which rests behind the ear, a receiver fitted at the ear-tip and thin earwire which connects the housing to receiver.
In the ear (ITE) hearing aids
"In the ear hearing" (ITE) aids are appropriate for most types of hearing losses, ranging from mild to severe. All the vital electronic components of the ITE are fitted inside the earmould.
ITE hearing aid is placed in the outer portion of the ear canal, with earmould customised to fit the shape of person’s ear. Though it is a tiny device, the faceplates are still visible in the concha or the ear. They also come with optional user programmable controls along with volume change on the outside of the faceplate.
Completely in the canal (CIC) hearing aids
"Completely in the canal" (CIC) hearing aid is the smallest hearing aid device appropriate for a person suffering from mild to moderate hearing loss. These are custom made as per the users requirements, with all the electronic components fitted in the shell. The shell is positioned deep inside the ear canal, making the device almost invisible. A CIC therefore has a cosmetic advantage, since it is invisible and no one can see the hearing aid.
Body worn hearing aids
Body worn hearing aids (digital or analogue) have a small box that can be clipped to clothing, belt or kept in pocket. Depending on the hearing loss they can be for one or both the ears. The body worn box contains all the electronic components which are connected to the earmoulds with the wires/leads.
This device is mostly appropriate for people with poor dexterity and who need a powerful hearing aid
Bone conduction hearing aids
Bone conduction hearing aids work on the same objective to amplify the sound, but the working principle is different than the conventional hearing aids. The sound is not passed via the ear canal, instead it is passed through the bone into the skull with the help of the bone conduction hearing aid.
Sound vibrations are transmitted directly from the hearing aid through the skull into the cochlea, bypassing the outer and middle ear, enabling person to hear.
Though not as efficient as hearing through air conduction, bone conduction hearing aids are suitable for people with conductive and mixed hearing loss, for whom conventional hearing aids provide little or no benefit. This includes people with:
- Chronic infection in the ear canal (external otitis)
- Absence or malformation of the outer ear, ear canal, or middle ear
- Congenital external auditory canal atresia
- And people with a single sided hearing impairment which are caused due to surgery for a tumour of the balance and hearing nerves (vestibular schwannoma)
Traditional bone conduction hearing aids are made up of device worn on the body and a bone conductor or vibrator attached to a removable headband. These devices can be uncomfortable to wear as they hold the headband tightly to your head (vibrating part). Alternatively the vibrating part can be fitted to the arm of specially made spectacles instead of headband.
Bone anchored device or bone anchored hearing aid (BAHA) is a surgically implantable system for treatment of hearing impairment that works through direct bone conduction. There is a seperate section for more information on Bone Conduction Hearing Aid (Baha).