9. Hearing aids, to the rescue! (Hearing aids and their types)
General Information on Ear & Hearing
The working of an ear is more complex than it appears to be. The journey of the sound starts from the Pinna which is channelled in to the tunnel like ear canal and vibrates the ear drum. The pinna and the ear canal constitute the external ear. The ear drum in turn moves a chain of 3 bones. . These are the smallest bones of our body and are a part of the middle ear. Vibrations are then passed on to the fluid filled inner ear or the shell shaped Cochlea. The Cochlea contains tiny sensory cells called hair cells which convert these vibrations in to electrical signals. The signals are carried to our brain by the Auditory nerve. When the signals reach our brain, Bing! We hear the sound and you would be amazed to know that all these phenomena occur in a jiffy. The inner ear also has three loop-like canals that help us balance in all our day to day activities.2. What is hearing loss?
Hearing loss is reduction in ability to hear/understand sounds and varies in severity from mild to profound. Depending on the part of the ear affected there can be three types of hearing loss. Any problems with the outer ear and the middle ear cause a conductive loss which can most often be reversed by medical treatment (Eg: Surgery). Problems with the inner ear (cochlea and the auditory nerve) will cause a sensori-neural hearing loss, this type is generally irreversible. Problems in inner ear and middle and/or external ear will cause a mixed hearing loss. Hearing loss affects all age groups although different factors contribute to the type and degree of loss. An approximated 7% of the Indian population suffers from hearing loss.
Most common indications of hearing loss are:
- Increasing TV/Radio/Music-player volume
- Asking people to repeat themselves
- Difficulty understanding speech especially in noise and group conversations
- Lacking clarity of speech
- Talking louder than usual
There are several professions involved in hearing health care. At the first stage you may see your doctor who would refer you to the appropriate professional- either an ENT specialist or an Audiologist depending on the problem.
Audiology is the study of hearing, balance and related disorders. The subject includes studying how the ear works and the various mechanisms in the ear that help us hear the world. It also includes measuring hearing (how well an individual can hear) and management of hearing loss, balance disorders, tinnitus etc. Hearing being a basic sense of all human beings seeks attention from all age ranges from a new born baby to the elderly.
The professionals who practice Audiology are called Audiologists. An audiologist will have a qualified degree in Audiology (BSc, MSc, AuD or a PhD). An Audiologist s work majorly involves measurement of hearing and diagnosis and management of hearing loss. Other professionals within Audiology include Hearing-Therapists and Audiological Scientists. Hearing-Therapists work in conjunction with Audiologists to improve overall communication skills various training (e.g. Lip/Speech reading). Finally, as the name suggests, Audiological Scientists carryout basic and clinical research in hearing sciences.
The most basic form of hearing evaluation is finding the lowest level at which an individual can detect sounds for various pitches. This can be performed using an Audiometer connected to headphones to test the 2 ears separately; this is called Pure-Tone Audiometry. These thresholds across various pitches/frequencies are plotted on a graph called an Audiogram. This test can gives information on the type and severity of hearing loss.
As mentioned above, hearing loss can occur due to a problem in the external ear, middle ear , and/or the inner ear.
Conditions of the External Ear
Wax: A build up of wax in the external ear canal can sometimes cause hearing loss. This condition would easily resolve when the wax works its way out by itself or when it is removed manually by a professional.
Infection of the external ear / canal usually does not cause hearing loss
Conditions of the Middle Ear
Glue ear: This condition is most common in children. This refers to a condition where there is fluid collection behind the ear drum. This can be caused by malfunction of the Eustachian tube (the tube that connects the middle ear and the back of the nose and helps in ventilating the middle ear). The fluid in the ear hampers the vibration of the bones and the ear drum causing a hearing loss. This condition resolves by itself in many cases but sometimes requires medical treatment (eg, insertion of grommet). Usually, hearing improves when the fluid clears. Sometimes, hearing aids are provided depending on the impact of hearing loss until the surgery. This condition is more common in the winter months.
Otosclerosis: This is a condition where there is excess bone formation/accumulation around the last of the three tiny bones (Stapes/Stirrup) in the middle ear. Conduction of sounds through the bones is reduced due to limited movement of the bones, leading to hearing loss. Individuals with this condition are given the option of correction by surgery or use of hearing aids. This condition is more common in females specifically getting worse during pregnancy.
In some conditions, the formation of the ear is either incomplete or is defective. This can also lead to hearing loss.
Conditions of the Inner Ear
Noise-Induced Hearing loss (NIHL): This is the damage caused to hearing due to exposure to loud noise either over a period of time or sudden exposure to very loud noises. The severity of the hearing loss can depend on the amount of exposure. Sometimes, the ear drum perforates causing a conductive loss or it could damage the inner ear's hair cells. The hearing loss is mainly sensori-neural. Hearing aid is one of the options depending on the hearing loss.
Oto-toxcitity: This refers to hearing loss induced by medication harmful to the ear. Medicines like the ''Mycin'' family, aminoglyosides, Aspirin (above 80mg on a daily basis) are a few examples.
Presbyacusis: Hearing loss that develops due aging (50 years +). This is sensorineural in nature and hearing aids are usually the only options.
Meniere's disease: This is a condition when the fluid balance is disturbed in the inner ear either due to over production or mal absorption of the fluid. This can cause short spells of severe dizziness, sea-roaring tinnitus and fluctuating hearing loss (mostly in one ear).
Genetic causes/ syndromes: Hearing loss can also occur due to genetic causes. Hearing loss, like many other diseases can be passed on from eneration to generation. Recently, many genes responsible for the cause of genetic hearing loss have been identified. Genetic counselling is a major tool in reducing gene related hearing impairment. Hearing loss can also occur with other gene related disorders like cleft palate and blindness.
Auto-immune disease: Auto-immune disease is a condition when one's body's own defences attack the organs of the body. Some of the Auto-immune diseases that can affect hearing include Cogan's disease, systemic lupus erythematosus, Wegener's granulomatosis, polyarteritis nodosa, relapsing polychondritis, temporal arteritis, and Takayasu's disease.
Sudden Sensori-neural hearing loss (SSNHL): A sudden drop in hearing ability of at least 30 dBHL within 3 days period causing a sensori-neural hearing loss is classified as SSNHL. This could be caused due to several reasons such as viral/bacterial infection, reduced blood supply, oto-toxic drugs, auto-immune disease, metastatic tumours, polycythemia, syphilis, leukemia and sickle cell disease. Studies quote that one third of the population affected by SSNHL recover to complete normalcy.
Hearing aids are devices that amplify sounds to make it audible for the hearing impaired. They are simple electronic devices with a microphone, an amplifier and a speaker. Most of the hearing aids available today are digital. Clinically, this essentially means that the hearing aids can be programmed very specifically to an individual hearing loss. There are different types of hearing aids depending on how large they are and how they fit.
When the hearing loss is so severe that conventional hearing aids are not useful, there is an option of surgically implanting a hearing device called cochlear Implant . This device directly stimulates the hearing nerve bypassing the whole ear.
CI is a prosthesis for hearing, not an amplification device as it does not amplify the sounds. When an individual's hearing loss is so severe/profound that he/she receives minimal benefit from even the most powerful hearing aids as well, CI are one of the options. The reason is total/near total loss of the sensory hair cells in the cochlea. The cochlear implant stimulates the nerve directly through electrodes inserted in the shell shaped cochlea, bypassing the hair cells. It consists of a microphone that sits behind the ear/ body worn and the signals are converted into electrical pulses, travel across the skull and is transferred to the electrodes in the cochlea which finally stimulate the auditory nerve.
Candidacy for CI is decided by running several tests. These can include PTA and speech testing with hearing aids.
In some individuals, conventional hearing aids increase the chances of ear infection as the mould occludes the ear thereby reducing ventilation.. Also, the discharge can easily block the sound outlet of the mould. Hence a hearing aid with a mould is not recommended in such cases. In such cases a BAHA or Bone Anchored Hearing Aid is prescribed. People with congenital malformation of the external or middle ear will also benefit from this device.
Here sounds are routed directly to the inner ear via bone vibrations. This device amplifies the sound and converts it into vibrations which are then passed on to the ''abutment'' or screw surgically fixed on the patient's mastoid bone/skull.
- Sound enters BAHA system
- Sound is amplified and vibrate the bone
- Vibrations reach inner ear
A ringing in the ear or Tinnitus is a common condition that everybody experiences at one time or the other. It varies from person to person and based on what actually is causing the tinnitus. Common descriptions of tinnitus include ringing, high pitched buzzing, hissing, humming, whistling or roaring. It may or may not be accompanied by hearing loss. It may be continuous or intermittent. In most people who experience it, appears to be louder or audible in the night or in very quiet situations. Some individuals find it very disturbing often affecting sleep and concentration.
The causes involve a large range of conditions, varying from wax to brain tumours. It often co-occurs with sensori-neural hearing loss, conductive loss, conditions involving balance, during oto-toxic medication and sometimes even anxiety and depression. People can experience tinnitus in either or both ears or in their head. Often, individuals exposed to loud noise/ music over a prolonged period tend to experience tinnitus before they experience hearing loss. Unless there is an obvious condition suspected to cause tinnitus, it is very difficult to pin-point the cause of tinnitus in each individual.
Most often when it is accompanied by hearing loss, wearing a hearing aid can relieve symptoms of tinnitus as using a hearing aid essentially reduces the silence due to hearing loss. There have been no medications which have been known to reliably reduce tinnitus. Most often, when the source of tinnitus is treated (For Eg removal of tumour which is causing tinnitus), tinnitus essentially stops. But in other cases, when the origin of tinnitus is questionable, the best way to fight tinnitus is to ignore it. Thinking about tinnitus and being conscious of a ringing in your ear can only make the condition worse. Often Audiologists/ hearing therapists help by advising ways to keep your brain occupied which helps in distracting you away from the tinnitus you perceive. Listening to music when you are in a quiet place can provide some relief. A healthy diet and regular exercises can sometimes help. Studies show that increased salt intake, increased level of alcohol in blood and smoking can cause/worsen tinnitus by interfering with the normal working of the ear. some people are prescribed to wear ''White noise masker'' to help distract from tinnitus. It is believed that using a masker for prolonged period of time can eventually reduce tinnitus. There are also ''bed-side maskers'' This is especially for people who find it difficult to fall asleep because of tinnitus.
Learn more about Tinnitus from LINK
Dizziness is actually a normal sensation that one experiences when the brain receives different messages from your inner ears or eyes. Dizziness may be linked to a problem with the ear or a symptom of a non-ear problems. There are conditions of the inner ear which lead to dizziness.
Acoustic-neuroma: is a benign tumour of the auditory nerve. It presents with all or at least 2 of the following- tinnitus, sensori-neural hearing loss and dizziness.
Labyrinthitis is an infection affecting the balance organ within the inner ear.
Benign Paroxsysmal Positional Vertigo (BPPV) is a condition caused due to displacement of certain crystals in the inner ear. An affected individual will feel dizzy only in certain body/ head position. Some repositioning therapies performed by Audiologists can often provide relief.
Learn more about Balance disorders from LINK
There are several devices available for individuals with hearing loss to assist them in day to day activities which involve hearing. they are called Assistive Listening Devices (ALDs). Below are some examples for ALDs.
Text telephone: this is recommended for individuals with severe hearing impairment and who face difficulties following conversations over the telephone. This allows phone conversations to be typed and read rather than spoken and heard.
Vibro-alarm: Most alarms ring. This can be difficult for individuals with hearing impairment. Whereas a vibro-alarm is tactile, they are often placed under the pillow which vibrates at the set time for alarm instead of ringing.
Induction loop systems: these work in conjunction with the ''Telecoil'' placed inside the hearing aid. In public places like cinema or a lecture hall, individuals with hearing impairment can often find it difficult to hear and understand what is being said because of echoes and other noises in the room. It is useful to have an induction loop that carries signals from the source (microphone) and relays electromagnetic signals in the room. The telecoil in the hearing aid picks up the electromagnetic signals and amplifies it for the hearing aid wearer. This way, the microphone of the hearing aid does not pick up the noise from the room or echoes in the room and this essentially means a noise free signal/speech for the hearing aid user.
The FM system works in a similar way. The advantage of the FM system is that it is wireless compared to the induction loop which requires the wires to be installed in the room. The hearing aid has an FM receiver which receives signals from the source.
There are many more ALDs with various modifications to adapt to different individual's needs. For more information on ALDs LINK
When it comes to ears, it is advised not to put anything smaller than your elbow inside, so certainly not ear-buds. Wax, when soft enough it will eventually make its way out on its own.
There are many things from which one needs to protect their hearing from:
One can buy commercial ear plugs which will keep ears out of water. Most hearing health care clinics also offer custom made ear plugs which offer a better protection; this prevents a condition called swimmers ears which is an infection of the ear canal. Most often hearing health care professionals recommend custom made ear plugs if someone has a ruptured ear drum to prevent chances of infection.
When exposed to sounds above certain loudness level over a period of time can cause damage to our sensory cells in the ear causing permanent damage called noise induced hearing loss. In case of noise exposure at work, wearing ear plugs/muffs damp the noise hence protecting the ear.
Listening to music at a high volume using head/ear phones over long periods of time can damage hearing. Try avoiding using personal music players in a noisy environment, as noise will mask the music. This increases the tendency to raise the volume level of the player to make it clearly audible. Noise cancelling ear/head phones are a better option in such situations. Remember, sound is just a pressure difference in the air, so it does not matter what head phones you use it is the amount of sound that reaches your ear matters when it comes to hearing loss.
Hearing protection devices such as ear plugs and ear muffs are commercially available which reduce the impact of noise on our hearing. It is highly advisable that people who work in a noisy environment wear such ear protection devices whenever they get exposed to loud noise. It is also advisable to get their hearing checked by an Audiologist regularly.
This depends on the cause of the hearing loss that runs in the family. If it is just the elderly people in the family have hearing loss, which would probably be just age related and not genetic. However, if a family member is hearing impaired since birth there may be some chance that the hearing loss could be passed on to your next generation. A blood test of the hearing impaired person and the parents-to-be might draw some information.