Types of hearing aids

Example of a bone conduction hearing aid
© bruckhoff hannover

Bone conduction hearing aids (BCHAs) are suitable for children who have conductive deafness. This could be caused by microtia (malformation of the outer ear), atresia (malformation of the ear canal), chronic ear infections or long-standing glue ear. They’re also suitable for mixed deafness or unilateral deafness.

Unlike behind-the-ear hearing aids, BCHAs vibrate in response to sound received by the microphone. These vibrations are then transmitted through the bones of the skull to the cochlea where they’re converted into sound in the usual way, therefore bypassing the outer and middle ear.

The transducer (vibrating part of the BCHA) sits behind the ear, usually on the mastoid bone (the large bone you can feel behind the ear). The transducer is held against the mastoid bone by a soft headband, a metal-sprung headband or, very occasionally, spectacle arms.

Children with profound unilateral (one-sided) deafness may benefit from a special type of hearing aid known as a CROS aid. CROS stands for 'contralateral routing of signal'. Although it’s described as a hearing aid, a CROS aid doesn’t amplify sound. It simply transfers sound from the deaf ear to the side of the hearing ear.

The main advantage of using a CROS aid is that it can help your child hear sounds from all directions.

A CROS aid includes two units which both look like ordinary behind-the-ear hearing aids. However, the unit worn on the deaf ear just contains a microphone. It’s connected to the other unit, usually by a wireless radio link. The child listens to the sounds picked up by the microphone through the second unit, which they wear on their hearing ear.

BiCROS aids are suitable when there’s no useful hearing in one ear and the other ear has some deafness.

In-the-canal hearing aid

Generally, in-the-canal (ITC) hearing aids are smaller and less noticeable than in-the-ear aids. The shell (which is custom-made for each user) fits into the canal part of the ear.

Because of their small size, ITC hearing aids aren’t suitable for young children. They may have fewer controls than other hearing aids and don’t have a direct audio input facility. However, some do have a T programme.

ITC hearing aids aren’t normally provided by the NHS.

In-the-ear hearing aid

All of the parts of an in-the-ear (ITE) hearing aid are enclosed in the shell, which is custom-made to the wearer’s ear and looks like an ordinary earmould. Most of the shell fits inside the ear, leaving the faceplate facing outwards.

Because all the parts need to fit inside the shell, the child’s ear canal needs to be large enough to take an in-the-ear hearing aid. Therefore, ITE hearing aids are more likely to be suitable for older children.

ITE hearing aids also are not suitable for more severe hearing losses as limitations on the technology and battery size mean that they can’t be manufactured powerfully enough. Your child’s audiologist will be able to tell you whether one would be suitable for your child.

ITE hearing aids are not routinely offered by NHS audiology services.

ITE hearing aids do not always have enough room for a telecoil and therefore have no access to a T programme.

Open fit hearing aids are behind-the-ear hearing aids that have special ‘open’ earmoulds.

Open earmoulds are made to fit from ear impressions in the same way as conventional earmoulds. They’re designed to channel sound into the ear canal without blocking external sounds around the wearer.

They’re most suitable for children with mild or moderate high frequency deafness because they allow natural hearing of low frequencies while amplifying higher frequencies. They aren’t suitable for more severe deafness as the amplified sound will leak from around the open mould and re-enter the hearing aid, causing feedback.

Alternatively, soft ear tips (also known as dome or mushroom tips) may be used. With soft ear tips, sound is channelled from the hearing aid to the ear canal using a very thin tube (microtube). This design is more cosmetically appealing to some wearers but may not be as secure in the ear as an earmould. This makes them suitable for older children or teenagers.

Receiver-in-the-ear hearing aids are also suitable for open fit technology.

Receiver-in-the-ear (RITE) or receiver-in-the-canal (RITC) hearing aids look similar to other behind-the-ear hearing aids. However, the ‘receiver’ (or speaker) is placed inside the ear canal instead of being housed within the casing.

Instead of a typical earmould, a thin electrical wire replaces the flexible tubing and connects the hearing aid to a small earpiece in the ear canal, housing the receiver.

An advantage of RITE hearing aids is that the microphone and receiver are further apart so there’s less chance of feedback. Also, because the receiver is removed from the hearing aid, the behind-the-ear part can be smaller, making it less noticeable.

However, they may be less secure to wear than a behind-the-ear hearing aid. The wearer will need to check the earpiece and receiver daily for wax to stop faults occurring. They aren’t suitable for people who have problems with discharging ears.

RITE hearing aids don’t have a direct audio input facility, although some do have the T (telecoil) programme. For these reasons, they are most likely to be used by older children or teenagers and are usually suitable for mild and moderate to severe deafness.

Spectacle aids combine a hearing aid into the arms of a pair of glasses. These aids are convenient for people who need to wear hearing aids as well as glasses all of the time. They are rarely used by children.

Two types of spectacle aids are available:

1. Acoustic aids – the aid is placed in the arm of the glasses, and the sound is carried to the ear by tubing and the earmould.
2. Bone conduction aids – the arms of the glasses provide pressure to maintain contact between a vibrating transducer and the mastoid bone.

Vibrotactile aids rely on the sense of feeling. They have a processor unit which picks up sounds through a microphone. A wire connects the processor to a vibrating transducer that responds to incoming sounds. The transducer is worn against the skin, on the wrist or across the chest, where the vibrations are felt.

Vibrotactile aids may be suitable for children who have little or no hearing and who would not benefit from using a more conventional hearing aid or cochlear implant.

A vibrotactile aid can give a child a sense of loudness, which helps them monitor and control their own voice level. It can also give a sense of the rhythm of speech and sometimes of the frequency of sounds.

Most hearing aids are 'water resistant', meaning they give some protection against sweat and any brief exposure to water. Water resistant hearing aids should not be immersed in water or worn when swimming or doing water activities.

Fully waterproof digital hearing aids are available for certain types and levels of deafness. Waterproof aids are great for active lifestyles as they offer protection, for example, at the beach, in the sea, at swimming pools, or on the playground.