Effects of noise on our hearing
In a world teeming with technology and incessant entertainment opportunities, noise can be a nuisance you cannot ignore or easily do away with.
From traffic to factories and even music, noise pollution has become quite common in major places.
Noise that pollutes the environment can either be loud and brief or loud and long lasting. Irrespective of the type, sound can damage the internal structure of your ears and cause what is usually referred to as noise-induced hearing loss.
Basic physiology of hearing
The ear receives sound, initially through the ear canal to the eardrum, through to the middle and inner ear and then onwards to the brain for interpretation.
A thin membrane (tympanic membrane), commonly called the eardrum, transmits the sound to the structures in the middle ear, essentially three tiny bones called the malleus, incus and stapes, collectively called the ossicles. The ossicles amplify sound approximately 1.3 times before it’s transmitted into the inner ear.
Since the inner ear contains fluids, this amplification of sound by the middle ear is necessary to match the change in resistance as the sound travels from air into the fluid-filled inner ear. This phenomenon is physiologically referred to as ‘impedance matching’ impedance and is necessary because it takes more energy for sound to travel through air than through a fluid.
The fluids are contained in a structure called the cochlea which is part of the inner ear and functions to transmit sound information to the brain in the form of complex nerve impulses. As the tympanic membrane vibrates in response to sound, it causes the ear ossicles to transmit those vibrations into the fluid-filled cochlea.
This fluid then brushes against tiny cells with hair-like projections, called hair cells, in the cochlea which are located in a tiny but highly complex structure called the Organ of Corti. When hair cells are stimulated by the fluid vibrations within the cochlea, they convert these vibrations into complex patterns of nerve impulses which are transmitted to the auditory cortex of the brain.
How sound damages your ear
The unit for measuring sound pressure is the decibel (dB). The eardrum is a very thin membrane. This means that intense sound pressure can make the eardrum vibrate to the point of rupture or tear.
When the eardrum is damaged, sound cannot be transmitted so effectively to the internal structures of the ear hence causing hearing loss. The ossicles in the middle ear can also be damaged by high intensity sound. Damage to the eardrum and/or middle ear causes so-called conductive hearing loss but rarely results total loss of hearing. However, the greatest effect of higher intensity sound is on the hair cells in cochlea (inner ear) which results in permanent, irreversible hearing loss especially for higher frequencies.
Noise-induced hearing loss (NIHL) can be immediate when the damage is caused by very high intensity sounds such as gunshots near the ear or explosions. More usually, NIHL results from prolonged exposure to higher intensity sounds such as in a noisy factory, being near loudspeakers at a music festival or nightclub or, increasingly, from listening to music at a high volume level on a smartphone.
Noise induced hearing loss can be prevented
Here is how:
- If you are unable to reduce the noise, simply get away from it.
- Use hearing protection, usually in the form of earplugs, if you know you are going to be in a very noisy place.
- If working in noise, always wear the highest NRR earplugs when working in areas with high noise levels. The highest NRR rating for earplugs (so far) is 33. NRR is Noise Reduction Rating and reflects how protective an ear plug is against noise.
- When listening to music through headphones or earbuds, don’t use a high volume setting.
Other effects of noise other than loss of hearing
- Tinnitus
- Alteration of sleep
- Poor performance and lack of concentration at work or school
- Overproduction of stress hormones in the body which can cause metabolic imbalances
- Alteration of speech
- Fatigue
You may not notice that you are losing your hearing ability. Noise exposure can result in slow but permanent changes in hearing sensitivity. All too often, hearing is irreversibly damaged before it becomes noticeable and you may regret it for the rest of your life.