How does noise damage the ears?
We are exposed to sounds every day, such as: television and radio, household appliances, and traffic. Usually, these sounds are heard at safe levels that do not affect our hearing. However, harmful noise (sounds that are too loud or loud sounds that last a long time) damages the sensitive structures in our cochlea, causing noise-induced hearing loss (NIHL).
These hair cells give us the ability to discriminate between different frequencies or pitches. So when the hair cells are damaged, the loudness of sounds is not affected. Rather, damage to the hair cells makes it difficult for you to distinguish different pitches of sound. For example, when listening to speech and you have:
Normal hearing, you will hear: “The quick brown fox jumps over the lazy dog and surprises it”
Hearing difficulty, you will hear: “‘e qui’ brown ‘ox jump’ over ‘e la’ dog and ‘upplies it”
Damage to the hair cells depends on the ‘dose’ of noise, that is the duration as well as the level of the noise. NIHL can either be caused by a one-time exposure to an intense loud sound, such as an explosion, or by continuous exposure to loud sounds over an extended period of time, such as noise generated in a factory with machinery.
The main thing to remember is that loud noise causes direct mechanical damage to the hair cells and once damaged, they cannot grow back.
What are the effects of noise-induced hearing loss?
Temporary or permanent hearing difficulty
Temporary or permanent tinnitus
Ringing in your ears
How do I know if I have noise-induced hearing loss (NIHL)?
When exposed to loud noise over a long period of time, symptoms of NIHL will increase gradually, so you may not be aware of the hearing difficulty to begin with. When it begins to affect your day to day life you may notice:
Sounds become distorted or muffled
Difficulty understanding speech
If you experience any of these symptoms you should have your hearing assessed - Contact The Art of Hearing for more information or for an appointment
Can noise-induced hearing loss (NIHL) be prevented?
Yes, NIHL is 100% preventable. You can prevent your ears from noise damage by:
Being aware of the hazards of noise and how to practice good hearing health in everyday life:
Keep the volume on personal headphones at a safe level
Stand away from loud speakers
If you don’t have ear protection, walk away from the noise or limit your time in noisy environments
Wearing custom made noise-plugs that are suitable to the noisy environment
Ensuring these plugs are also suited to your level of hearing
Creating awareness and spreading the word. Inform family, friends, and colleagues of the hazards of noise
Note: the above information is for guidance only. Exposure to levels above 70-80dB can damage your ear permanently.
If you suspect you have a hearing loss or tinnitus Contact The Art of Hearing for more information or for an appointment.
Types of noise-plugs available
Sponge /disposable noise-plugs
Standard / non-custom noise-plugs
Custom made noise-plugs
How are custom earplugs or custom noise-plugs made
- Presence of earwax:
An impression cannot be taken with wax in your ear. The audiologist will need to remove the wax first.
- No earwax:
move to step 2
A small foam block placed in your ear
Using a special syringe, the audiologist will fill your ear canal with a silicone putty
The silicone will be left in your ear for a few minutes to set and once set will be carefully removed from your ear
The impression of your ear will be sent to a manufacturer to be made into the earplug that was chosen for your individual needs
Certain conditions of the ear will influence whether the impression can be taken or not. So it is vital that only a qualified audiologist examines your ears, and takes the impressions.
Structures of the ear and hearing
The ear is the part of the body responsible for hearing and balance. Only vertebrates (animals with backbones) have ears. Invertebrate animals, such as jellyfish and insects, lack ears, but have other structures or organs that serve similar functions. The most complex and highly developed ears are those of mammals. The ear does not work in isolation, it transmits sounds via the auditory nerve to the brain.
The human ear consists of three sections: the outer, middle, and inner ear. The outer and middle ears function only for hearing, while the inner ear is also responsible for your balance and orientation.
The outer ear
The outer ear is made up of the pinna, the external ear canal and the outer part of the eardrum.
The pinna is a cartilaginous part of the ear attached to the side of the head. It acts as a funnel that collects sounds from the environment and transfers it into the ear canal.
The ear canal is a tube-like passage that measures about 3cm in length. It leads from the pinna to the eardrum. The first part of the ear canal is lined with delicate hairs and small glands that produce wax. Wax prevents dust and dirt from entering the deeper part of the ear. The inner two-thirds of the ear canal is surrounded by the temporal bone of the skull, which also surrounds the middle and inner ear. The temporal bone protects these fragile parts of the ear.
The eardrum separates the outer ear from the middle ear. It is a thin, round, skin-like membrane that is stretched tight like a drum across your ear canal. When a drummer beats a drum, the drum vibrates to make sounds – similarly, sound hits the eardrum and causes it to vibrate. The eardrum amplifies the vibrations of sound so it can travel from the tiny bones of the middle ear, which then sends the vibrations into the inner ear.
The middle ear
The middle ear is a narrow, air-filled chamber about 1.5cm cubed in size. The middle ear has 3 main parts: the inner part of the eardrum, the ossicles and the eustachian tube.
The inner part of the eardrum is attached to the middle ear by the first bone of the ossicular chain, the malleus. The ossicles are the tiniest bones in your body - each about the size of a grain of rice. They each have a unique name based on the shape; the malleus or hammer, the incus or anvil and the stapes or stirrup. These 3 bones are responsible for transferring sound from the eardrum to the inner ear. This is because the last bone, stapes, is attached to the cochlea. These bones also have a function to protect the ear.
A narrow passageway called the eustachian tube connects the middle ear to the throat and the back of the nose. The eustachian tube helps keep the eardrum intact by equalising the pressure on either side of the middle and outer ear. For example, if you are in an airplane while taking off, the air pressure becomes lower as the plane climbs higher in altitude. Your ears may feel some discomfort at this point because the air pressure in the middle ear becomes greater than the pressure in the outer ear. When you yawn or swallow, the eustachian tube opens, and some of the air in the middle ear passes into the throat, adjusting the pressure in the middle ear to match the pressure in the outer ear. This equalising of pressure on both sides of the eardrum prevents it from rupturing.
The ear’s protective reflex
An acoustic reflex is the protective mechanism of your ear. When loud noises produce forceful vibrations, two small muscles called the tensor tympani and the stapedius, contract and limit the movement of the ossicles. This is similar to when you instinctively pull your hand away from a hot plate. This action reduces the intensity of the sound that enters the main organ of hearing (cochlea) and thus reduces damage to your ears.
Tensor Tympani Muscle
The inner ear
The inner ear contains the main organs of hearing (cochlea) and balance (the vestibule and the three semi-circular canals)
The cochlea is the main organ of hearing. It is a coiled tube about the size of a pea and looks like the shell of a snail.
The cochlea is filled with fluid and within this tube are rows of tiny sensors or hair cells responsible for hearing. These hair cells give us the ability to discriminate between sounds of different pitch or frequency.
Vestibule and semi-circular Canals
The vestibule helps the body maintain balance by detecting changes in gravity and linear acceleration (i.e. standing up or lying down or feel acceleration when you move in a car). The three semi-circular canals also direct your body balance when the body moves in a straight line or rotates in any direction.
The acoustic nerve and the brain
This is the nerve that is responsible for hearing, balance, and head position. Its primary function is to transmit sounds from the inner ear to the brain. It has two parts: a cochlea part (auditory) that transmits sound reception for hearing and a vestibular part (balance) that senses balance and head position.
It is in the brain that sounds are identified, processed and understood (auditory processing). The part of the brain responsible for auditory processing is called the temporal lobe. Both ears work together to identify sounds from all around us. This gives the brain the full information in order to identify the type of sound and which direction it is coming from.
The temporal lobe is known as the primary auditory cortex (the first part of the brain that receives sounds from the ear). It is the main part of the brain responsible for understanding written language, spoken language and speech discrimination. It also maintains long-term memory.
How do structures of the ear enable us to hear
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Degree, type and configuration of hearing difficulty
Hearing thresholds are measured in decibels and are plotted on an audiogram for frequencies from 250Hz to 8000Hz. Thresholds are explained using descriptors related to severity (audiogram showing severity of hearing loss):
normal hearing (up to 20 dB HL),
mild hearing loss (21 to 40 dB HL),
moderate hearing loss (41 to 70 dB HL),
severe hearing loss (71 to 95 dB HL),
profound hearing loss (96 dB HL or greater).
Type of hearing difficulty (the origin/source of the problem)
Hearing difficulties may be described as conductive, sensorineural or mixed. This section refers to the part/s of the ear which cause your hearing difficulties.
A conductive hearing difficulty is one that affects the structures that conduct the sound to the inner ear - this includes both the outer and middle ear.
Conductive hearing difficulty can be caused by wax build up, fluid in the middle ear, perforated eardrum or damage to the middle ear bones. Build-up of earwax can easily be removed. See ear hygiene and earwax removal. You will generally need to be referred to an Ear Nose and Throat consultant to treat the other types of conductive hearing loss - an infection can be treated with antibiotics, a ruptured eardrum can be surgically patched and damaged middle ear bones can be surgically replaced or reconstructed.
A sensori-neural hearing difficulty is one that affects the structures that transfer sound from the main organ of hearing (cochlea), to the hearing nerve (auditory nerve), which then conducts sounds to the brain (central nervous system).
Sensory hearing difficulty originates in the inner ear (cochlea) and neural hearing difficulty originates from structures or systems beyond the inner ear (e.g. the auditory nerve or the central nervous system).
SNHD is caused by loss or damage to the hair cells in the cochlea. Some common examples of this are:
Age-related hearing difficulty (presbycusis): Many people experience a natural decline in hearing as they get older
Noise-induced hearing difficulty: Long-term exposure to loud sounds or experience of one very loud sudden sound
Viral or bacterial infections: Infections such as mumps or meningitis
Ototoxic Medication: Some medication in high doses such as those for infectious diseases
Other neurological conditions such as dementia, multiple sclerosis, stroke, brain injury or brain tumours affect the brain and/or the central nervous system. This causes hearing difficulty whereby sounds are transferred to the brain but cannot be understood or processed.
Mixed Hearing Difficulty
A combination of conductive and sensori-neural is called a mixed hearing difficulty. This means that the outer, middle and inner ear all affect the hearing.
Configuration of the hearing difficulty (qualitative information)
Gradual / progressive or sudden onset
High frequency or low frequency
Stable or fluctuating
Symmetrical (same level in both ears) or asymmetrical (different level in each ear)
Unilateral (one ear) or bilateral (both ears)
What is an audiogram?
An audiogram is a chart that displays information about your hearing sensitivity. The y-axis (shown vertically) represents loudness measured in decibels (dB) and the x-axis (shown horizontally) represents frequency measured in hertz (Hz). It shows your hearing thresholds for each of the frequencies tested. The decibels are listed from top to bottom starting with 0dB and stopping at 120dB. The frequency starts on the left side at 125Hz and goes up to 8000Hz.
Frequency or pitch
The audiogram’s x-axis represents frequency in Hertz (Hz). The lowest pitches start of the left side to the very highest frequencies on the right side. The range of frequencies tested are usually 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz and 8000 Hz, as these are the main frequencies for speech perception.
Examples of low frequency sounds in everyday life are: low rumbles, bass drum and vowel sounds.
Examples of high frequency sounds in everyday are: sizzles, bird chirping and consonant sounds
Loudness or intensity
The audiogram’s y-axis represents intensity of sound in units of decibels (dB). The top of the chart signifies soft sounds and the bottom of the chart signifies very loud sounds.
Examples of soft sounds in everyday life are: clock ticking or whispering.
Examples of loud sounds in everyday life are: lawnmower or car horn.
Normal conversational loudness level is between 40-60dB and whispering approximately 30dB.
The audiogram configuration may have:
Flat - equal hearing difficulty in low and high frequencies
Sloping down - better hearing in the low frequencies
Rising - better hearing in the high frequencies.
The configuration may show the same hearing difficulty for both ears or different hearing difficulty in each ear.
Will my hearing get worse if I don’t wear hearing devices
When trying to answer this question, it is important to remember that we hear with both our ears and our brain. A hearing difficulty generally occurs gradually over a period of time, and you may not notice it in the early stages. This means that your hearing pathways (i.e. nerves from your ear to your brain) are not being used as much as they could be. Your brain does not receive as much stimulation as someone with normal hearing. The longer your hearing pathway goes without being stimulated, the more risk there is of nerve pathways wearing out – this is referred to as auditory deprivation.
Our bodies are very efficient and if you are not using something, your body will stop sending signals to that part. For example, if you were to keep your hand in a sling for 10 years and not use it, it would become very difficult for you to start to use the hand again. This is because your body would recognise that all of your muscles, ligaments and nerves, usually used to move your hand are not being used. So your body uses its energy on parts of the body that are actually being used and not wasting energy on parts that are not being used. Thus, when referring to hearing “use it or lose it” is an accurate description.
Research has shown that people with hearing difficulties usually wait about 7-10 years to assess their hearing. This is because hearing loss occurs gradually and is initially not noticed. Furthermore, there is a stigma attached to hearing loss, so when individuals notice hearing difficulty they put off the decision to seek help. This delay in seeking help means that you have not used your hearing pathways for about that same period of time. As a result, your brain’s ability to understand speech, especially in noisy settings, becomes increasingly difficult. When you finally decide to try hearing devices, the initial benefit is not perceived because your hearing pathway has not been used for such a long time.
The important thing to remember is that just as you would need to have regular physiotherapy, regularly do exercises and progressively increase the strength of the exercises to get your hand working again – you would need to use hearing devices first in quiet environments and then slowly work the use up to noisy environments.
A large body of medical research has proven that untreated hearing loss can lead to a deterioration of your hearing pathways, and this can increase your risk of mental decline and dementia. If you have hearing difficulty, it is vital to use hearing devices so that these pathways are continually stimulated, healthy and active. A report on prevention of dementia states that if hearing loss is treated (with hearing devices) in mid-life, it can prevent the onset of dementia (Lancet Report, 2018).