Ultimate guide to hearing and hearing loss
The ear is a very sophisticated organ, which is made up of a number of important structures. The ear is made up of three parts; these are:
- The inner ear
- The outer ear
- The middle ear
Hearing and audiology is based solely on physical movement, rather than chemical reactions.
The structure of the ear
Sound enters the ear through the outer ear and travels down the ear canal into the eardrum; the sound starts to vibrate once it enters into the middle ear. The middle ear is a cavity, which is filled with air; the middle ear is connected to the inner ear. The inner ear contains the cochlea, which is a fluid-filled, spiral shaped structure and the vestibular system, which helps to control balance.
Sounds enter the ear via the outer ear and are gathered by the eardrum (also known as the tympanic membrane). The eardrum passes the sounds down the ear canal into the ossicles, which are the smallest bones in the body (these are called the malleus (hammer), incus (anvil) and stapes (stirrup); the waves are then diverted to the cochlea. The cochlea is divided into three different fluid-filled chambers, which are receptive to different sound frequencies. The sound signal is then converted into an electrical impulse, which travels to the cochlear and vestibular nerves. The electrical impulses are interpreted as sounds in the auditory cortex of the temporal lobes in the brain.
Hearing may be affected if there is a problem with the function or structure of component parts on the ear. If there is blockage or the ear is infected, for example, the ear may not work in the normal way and the individual’s hearing will not be as good as usual. You can find out more about hearing from a specialist in audiology.
It is estimated that 1 in 5 people in the UK experience difficulties with hearing. Some people suffer from temporary hearing loss, while others are born with hearing impairment and some people experience permanent hearing loss as a consequence of a health condition or accident.
Types of hearing problem
There are many different types of hearing or audiology problems, which may contribute to either temporary hearing loss. There are two main types of hearing loss; these are:
- Conductive hearing loss: this occurs when sounds cannot travel from the outer to the inner ear; this is usually the result of an obstruction or blockage.
- Sensorineural hearing loss: this occurs when the hair cells inside the auditory nerve or cochlea are damaged; this may be caused by ageing or as a result of trauma or an accident.
Hearing impairment may be classed as mild, moderate or severe.
What causes hearing problems?
There are many possible causes of audiology problems; these include:
Causes of conductive hearing problems:
- A build-up of ear wax
- Glue ear: this is a condition, which occurs when fluid collects in the middle ear
- Ear infection, also known as otitis media
- An obstruction, such as a foreign body
- A burst eardrum
- Otosclerosis: this is a condition which occurs when an irregular enlargement of bone starts to form in the middle ear
Causes of sensorineural audiology problems:
- Ageing (this is known as presbycusis): many people experience hearing loss as they get older. This is usually due to the natural deterioration of the sensitive hair cells in the ear. Most people start to experience hearing loss from the age of around 40.
- Exposure to loud noises (this is known as acoustic trauma): the ear may be damaged as a result of long-lasting exposure to loud noises. This is common amongst people who work in noisy environments, such as musicians, construction workers and nightclub staff, but it may also be common in people who listen to music very loudly through their headphones.
- Infection: viral infections of the inner ear, such as mumps or measles and the auditory nerve, such as rubella and mumps, may affect hearing.
- Acoustic neuroma: this is a non-cancerous tumour, which grows on or around the auditory nerve.
- Encephalitis: this is a condition, which causes the brain to become inflamed.
- Meniere’s disease: this is a condition, which affects the area of the ear commonly known as the labyrinth.
- Multiple sclerosis
Deafness and audiology problems in children may be caused by inherited conditions, which may be associated with the development of the cochlea, chromosomal disorders or infections during pregnancy.
When are hearing tests carried out?
Hearing tests are usually carried out for two reasons; firstly, they are done on newborn babies and young children as part of routine developmental tests and secondly they are done when an individual is experiencing difficulties with their hearing or has a hearing impairment.
Hearing tests for newborn babies are carried out in the first few weeks after the baby is born. If there is a problem with the baby’s hearing, further tests may be required and the baby will be referred to an audiology specialist.
Hearing tests are usually carried out in adults when an individual has symptoms of hearing loss or problems with their hearing or balance; these may include:
- Tinnitus (ringing ears)
- Soreness and pain in the ears
- Dizziness and problems with balance
- Fluid or blood coming out of one or both ears
Hearing tests may also be carried out if an individual has suffered a head injury.
Why are hearing tests ordered?
Hearing tests are ordered for all babies in the UK as part of their routine set of developmental checks. It is important that hearing problems are diagnosed as early as possible so that the child can receive the appropriate treatment. In the past, many children with hearing problems were not diagnosed until the age of 18 months. However, the introduction of routine audiology tests for newborn babies has meant that many children have been diagnosed and subsequently treated much earlier. Early diagnosis is important because hearing plays an important role in a child’s development.
Adult hearing tests are used to test for hearing impairment. Many people may have impaired hearing without even realising it because hearing loss is usually a gradual process. Some hearing problems cause temporary deafness, while others may contribute to permanent hearing loss. Once the cause of the problems has been identified, an appropriate course of action can be determined.
What happens during an audiology test?
As part of the Newborn Hearing Screening Programme, all newborn babies in the UK are tested; the otoacoustic emissions test (OAE) is usually used for newborn babies. The OAE test requires the insertion of a small probe into the baby’s ear. The probe makes a subtle noise, which causes the baby’s ear to produce a corresponding noise; this echo is recognised as the otoacoustic emission. The sound made by the baby’s ear (the otoacoustic emission) is measured by a computer. Most babies who can hear will register this sound, while some babies may not produce a sound the first time and the test will be repeated if necessary. The OEA test is very simple and painless and takes just a few minutes to produce a result.
In some cases, the ABR (auditory brain response) audiology test may be carried out, which involves measuring the child’s response to sounds which are played through earphones.
Adult hearing tests also include a physical examination of the ear. This is to check for obstructions, damage to the structures of the ear or symptoms of conditions which may be causing problems with hearing. Additional tests include the whisper test (when the doctor or nurse whispers in the patient’s ear, with the other ear blocked), the tuning fork test (this involves holding a tuning fork to the ear to determine how well the individual can hear sounds that are transmitted through the air) and the audiometry test; this involves the individual listening to different sounds and saying whether or not they can hear the sounds.
Hearing aids are small devices, which are used to help people who are hard of hearing. Hearing aids can be worn either inside or outside the ear to improve audiology. Some are fitted inside the ear, while others sit behind the ear. Hearing aids are made of up three main component parts, including:
- a microphone
- an amplifier
- a speaker
Types of hearing aid
There are many different types of hearing aid; these include:
- Behind the ear hearing aids (BTE): these hearing aids have an earmould, which sits inside the ear. The external part of the hearing aid is attached to the earmould and sits behind the ear.
- In the ear hearing aid (ITE): in the ear hearing aids sit inside the ear and are not clearly visible.
- Completely in the canal hearing aids (CIC): completely in the canal hearing aids are even more discreet than ITE hearing aids. They are not suitable for people with very severe hearing problems.
- Body worn hearing aid (BW): this type of hearing aid consists of a small box, which can be attached to clothing or placed inside a pocket.
- Bone conduction hearing aid: this type of hearing aid is recommended for people who cannot wear other types of hearing aid and people who have conductive hearing loss. Bone conduction hearing aids work by vibrating in response to sounds.
How do hearing aids work?
There are now different types of hearing aid available that improve audiology; these include analogue and digital hearing aids.
Analogue hearing aid
Analogue hearing aids convert sounds into electrical signals, which are made louder by the amplifier component of the hearing aid. The hearing aid can be customised to suit the individual; the settings will usually be determined based on advice from the audiology specialist.
Digital hearing aids
Digital hearing aids are becoming increasingly common and almost all NHS patients are now given digital hearing aids, rather than analogue hearing aids. Digital hearing aids work by converting sounds into sets of numerical codes, which are then amplified; the information is then processed by a very tiny computer. The hearing aid can be adjusted and adapted to suit different environments and surroundings.
How do I choose which type of hearing aid I have?
It is best to discuss different types of hearing aid with your audiology professional. They will be able to explain the difference between the different types of hearing aid and recommend a hearing aid which is suitable for your individual prescription. Some types of hearing aid are not suitable for some people so it is always best to get professional advice.
Hearing is something that many of us take for granted but some people lose the ability to hear and others never get the opportunity to hear because they are born with severe hearing problems. Hearing or audiology is a very valuable sense, which enables us to communicate with other people, participate in certain activities and appreciate the amazing array of sounds and noises available to us on a daily basis. For many people, losing their hearing or sense of audiology is a bitter blow and it can be difficult to adapt to life without the ability to hear.
Support networks and charities
There are a number of support groups and charities, which provide support and advice for people with severe hearing problems; these include:
- The British Deaf Association
- Hearing Concern
- Deafness Research UK
- National Deaf Children’s Society
- Hearing Dogs for the Deaf
Equipment and practical help
There is equipment available to help people with severe hearing or audiology problems. Examples include special door bells and alarm clocks, specially trained dogs for deaf people, text phones and telephones with visual screens. People with hearing problems will be offered help by occupational therapists to ensure their home is safe and enable them to communicate with others.