Aids & Appliances

Type of Hearing Aids, It’s Care Maintenance

Types of Hearing Aids

Pocket Model:

Worn in a pocket or harness at chest level. It consists of the body of the hearing aid containing the microphone, amplifier and controls. A cord transmits the electrical output to a receiver, which converts this signal into sound. The receiver is attached to a mould, which holds it in place.

Behind the Ear (BTE):

The body of the instrument is worn behind the ear. It ‘hooks’ over the pinna. It is attached via plastic tubing to an earmould, which holds it in place in the ear.

In the Ear (ITE):

The complete hearing aid is in the ear or ear canal. The hearing aid is housed in a hard plastic shell which is often custom made by taking an ear impression.

Spectacle Type:

The hearing aid components are incorporated within a spectacle frame. It is useful for persons who require glasses along with hearing aids.

Bone Conduction (BC) hearing aid:

This is used when the ear canal is blocked or in cases where conventional amplification as described above cannot be given. A BC vibrator is placed on the mastoid bone behind the ear. It converts the amplified electrical signal into vibrations. BC vibrator can be used with body level, BTE or spectacle hearing aids.

Hearing aids should always be used with custom-made ear moulds. Ear moulds are devices, which couple the hearing aids to the ear. Ear moulds can be of hard or soft material.

Different Types of Hearing Aids Available in The Market:

Please Note:

• Hearing aids have different ‘Powers’ and ‘features’. The hearing aid which has the ‘right’ power and features for a particular user will provide maximum benefit. Therefore, hearing aids should always be purchased after under going a trial.
• Hearing aids can be worn in one ear or both ears according to the hearing loss.
• The best performance of the hearing aid can be obtained only when you use the hearing aid with ear moulds made for your ears.
• The hearing aids may be simple ‘analog’ type or they may be digital. Digital hearing aids are much more expensive.
• Hearing aids run on batteries. The life span and cost of different types of batteries are as follows:

Details of different types of batteries

Care Maintenance of Hearing Aids

Tips For Hearing Aids Care:

• Prevent it from falling down
• Don’t spill liquids on the hearing aid
• The hearing aid should be fitted well – pocket model aid in a harness and BTE with appropriate moulds and retainers if needed.
• Cords should not be twisted or knotted.
• Protect it from dust, dirt heat.
• Remove the battery from the hearing aid when it is not in use.
• Remember to detach the earmould from the receiver before washing the mould. The receiver should not come in contact with water.

Trouble Shooting for Body Worn Hearing Aids:

Trouble Shooting For BTE Hearing Aids:

Caution

The trouble shooting chart aids to give you tips to solve only very simple practical problems. If you cannot rectify the problem using the methods suggested, do not try to do any repairs on your own. Go to a qualified electronic technician or your hearing aid dealer/service agent. Hearing aids will last longer and provide better sound quality if they are regularly serviced and any problems rectified at the earliest.

Care Maintenance of Ear Moulds

• Keep the moulds clean and free of dirt or ear wax. Blocked moulds result in poor sound reception. Dirt may lead to infection in the ear.
• Wash the ear mould in soapy water and clean the dirt with a wire or tooth brush. Use it only after it dries completely.
• Do not press the mould hard over the receiver (in pocket model aids) as this can damage the receiver.
• Replace moulds when they become loose/child can not wear the hearing aid at the normal volume level due to a squealing sound. In young children, moulds may need frequent changing (some times even once in 4-6 months) as the size and shape of ear canal changes with growth.
• The mould should not be removed very often from the receiver as the spring loses its tension. However remember to detach and remove the receiver before washing the earmould.
• The mould should be properly seated in place so that no sound leakage is present. If the mould is slightly loose, a little cotton, sponge or fabric may be placed in between the receiver and mould for tight sitting and sealing. This would also minimize the sound leak.
• If the child shows any skin reaction after using the mould consult the ENT specialist.

Assistive Listening Devices

These are special systems which are designed to assist people with hearing impairment for specific purposes such as using telephones, watching/listening to TV, doorbell, alarm clock etc. They by and large facilitate auditory activities of daily living.

They refer to system that

• Enhance only the signal (sound which is useful for the person) and not the noise by transmitting amplified sound directly to the listener with hearing impairment.
• Transform sound into visual or vibrational signals

Sound Enhancement Technology

Sound Enhancement Technology systems used to assist in the reception of sounds. Eg. Personal and group hardwire systems, infrared systems, loop induction systems and frequency modulation systems.

In these systems, microphones picks up sound (incoming) and convert it into another form of energy. An amplifier then increase the intensity of this signal. Lastly a receiver converts the amplified signal back into acoustic (sound) energy so that the person with hearing impairment can hear it.

Induction Loop Systems

In Induction Loop Systems the amplified electrical signal is made to run through a loop of wire which may be enclosed in the walls of the room or worn as a neck-loop by the user. The electromagnetic field generated around the wire can be picked up by the hearing aid kept in ‘T’ (telecoil) position and reconverted to amplified sound which the person with hearing impairment can hear.

These systems have been installed at ticket booking counters of railway stations in some of the major cities of India. This would enable the person with hearing impairment to hear announcements made over the microphone without being disturbed by the noise. The listener would have to wear his own hearing aid set it to ‘T’ position. Induction loop systems are also used commonly in special schools for the hearing impaired.

Group Hearing Aids

Group Hearing Aids are generally used in classrooms of special schools for children with hearing impairment. The teacher has microphone with him/her. The amplified signal is fed to earphones worn by the children sitting at their desks. Each earphone headset has a volume control adjustment on it or on the desk. There are microphones fixed to the desks so that whatever is spoken by one child can be heard by the others.

Frequency Modulated (FM Systems)

FM Systems are probably the best systems to combat the effects of noisy environment. The sound signal is picked up by the microphone (used by the person speaking) amplified and converted into a radio frequency modulated carrier waves. They are transmitted to a personal receiver worn by the person with hearing impairment. The receiver converts the signal to audible sound.

These systems provide very good sound clarity even in the presence of room noise. FM systems are however, expensive.

Infrared Systems

In Infrared Systems the sound picked up by the microphone is converted into infrared light waves, which are then dispersed throughout the listening environment. A special receiver is worn by the listener, which converts these light waves backs to sound. These systems give good sound clarity but have drawbacks including cost.

Television Enhancement Technology

Television Enhancement Technology equipment is used to improve auditory perception of a televised signal. Also caption decoding can be done.

They include different types of devices. Some of them are targeted to improve sound quality for the listener. Infrared systems can be used for this purpose.

Closed caption decoders are also very useful as they convert all the spoken messages on TV into visible text/captions which can be read on the TV screen.

Telecommunication Technology

Telecommunication Technology systems used to enhance telephone communication. Eg; Text telephone, built-in portable amplifiers and induction loop systems.

These include systems designed to make communication over the FM telephone easier for the person with hearing impairment. A hearing aid user can keep his personal hearing aid on ‘T’ position to listen over the telephone.

There are special hand sets which give amplified sound. Some manufacturers produce telephone couplers which can be attached to regular handsets to get amplified sound.

Text Telephones/Telephone devices/Teletype writers:

Both parties communicating must have the instrument. One person types the message. The signal is transmitted through the telephone line and displayed on the screen of the person receiving the message.

Signal/Alerting Technology

Signal/Alerting Technology use devices which delivers signal through visual or tactile vibratory means so as to enable hearing impaired person to perceive them.

This includes technology to alert persons with hearing impairment to the presence of sound by converting the sound into another form of energy (visual/vibration) which she/he can perceive Eg. Alarm clock with vibrators, baby cry systems for hearing impaired parents, door bell/telephone alerts, smoke alarms.

Tips on Hearing Aid Selection

Different Types of hearing aids provide different advantages and disadvantages. The client must choose which hearing aid he/she wants based on the audiologist’s advice and their own decisions after weighing the pros and cons. Body level hearing aids are sturdy, less expensive to buy and maintain. They also have lesser problems of feedback squeal if the earmoulds are not good. The disadvantages are that

• the microphone is chest mounted and does not give ear level hearing.
• there is a difficulty in eliminating the effects of cloth rubbing noise and body shadow (the body may block some sounds from reaching the microphone).
• there is a difficulty in providing advantages of binaural hearing such as localization.

BTE hearing aids are more expensive to buy and maintain. They are small and thus easy to wear in children. They offer more flexibility with respect to adjustments in the output signal. BTE provide the advantage of binaural hearing as sounds are received at normal ear level. Localisation of sounds is easy compared to even 2 pocket model hearing aids.

In the ear and in the canal hearing aids also provide advantages of binaural amplification. They are expensive and not worthwhile for children because the entire hearing aid will need to be recased if the size and shape of the ear changes. In BTEs and pocket model aids, only earmoulds need to be changed. ITEs are also not useful for profound hearing losses. In the canal hearing aids fit in the ear canal and make use of the natural resonant properties of the external ear.

It is important to remember that irrespective of which style of hearing aid is chosen (BTE or pocket level) auditory training is required because that is what largely determines the child’s progress.

Solar Battery Charger for Body Level Hearing Aids

Solar Battery Charger for Body Level Hearing Aids is developed under Mission mode project scheme funded by Ministry of SJE, Government of India.

The Solar Photovoltaic battery charger is designed to charge a Nickel–Cadmium battery. The charger is designed for a very long life use of almost 12 years. Two batteries supplied with the charger will last for minimum four years of continuous use.

The Solar Photovoltaic battery charger for body level hearing aids is supplied with the following:

• Solar photovoltaic charger
• 2 Nos. 1.2 V Nickel Cadmium Battery