From Sound Wave to Hearing

Hearing is one of the five basic senses. It enables us to...
communicate and receive information, enjoy the sounds of nature and listen to music. All sound originates from movement. When, for example, the wind blows, it causes the leaves on trees to move. The leaves push the molecules in the air, making them vibrate. These vibrations are called sound waves and can be perceived by the air. Slow vibrations (low frequency) are heard as deep tones (bass), while fast vibrations (high frequency) are heard as high tones (treble).

The Human

The ear is a sophisticated, sensitive and complex organ...
which consists of three main sections.



The Outer

The outer ear is made up of the external cartilaginous part...
of the ear and the ear canal. The eardrum is located at the end of the ear canal and forms the boundary of the middle ear. The outer ear functions as a kind of satellite dish that picks up sound waves and conducts them to the eardrum, causing it to vibrate.

The Middle Ear

The middle ear is an air-filled space that connects the outer ear...
canal to the inner ear. It starts with the Tympanic Membrane (eardrum); it also contains the bones of the middle ear, and then ends with the oval window of the cochlea. The tympanic membrane is a cone shaped layer of tissue at the end of the ear canal. Sounds travel down the ear canal and strike the tympanic membrane causing it to vibrate. These vibrations are then transferred to the chain of bones in the middle ear. The middle ear bones are the smallest bones in the human body and are very delicate. Muscles and ligaments hold this fragile chain of bones in place and allow them to vibrate back and forth with sounds. The first bone in the chain is called the Malleus (hammer), the second is called the Incus (anvil), and the last bone is called the Stapes (stirrup). The sound vibrations cause the Stapes to move back and forth. This motion is thus transferred to the inner ear.

The Inner Ear

The inner ear, or cochlea, is shaped like a snail shell and filled with fluid...
The balance organ is attached to the cochlear and is made up of three fluid-filled semi-circular canals. The oval widow connects the middle ear and the inner ear. The footplate of the stirrup is attached to the oval window and functions as a piston moving the fluid of the inner ear. This movement of the fluid activates the hair cells in the inner ear (there are about 20,000 of these “sensory cells”). When the hair cells are activated, they send impulses via the acoustic nerve to the brain, which perceives these impulses as sound. Via these fantastic, winding ways, the ear is able to pick up sound waves, transform them to bone vibrations then to move movements in fluid and finally to nerve impulses that can be interpreted by the brain. Even the slightest flaw in this complex system can compromise hearing ability.

Hearing Impairment

Millions of people worldwide are faced with hearing problems...
in the form of hearing loss or tinnitus (ringing or other sounds in the ear), but only a minority of them wear hearing aids. Hearing loss is not just an age-related problem but affects people of all ages including, to an increasing extent, young people. Physiological age-induced hearing loss is, however, still the most common type of hearing loss.


Sensorineural hearing loss is due to a problem in the inner ear...
or cochlea. The inner ear does not change sound into the tiny electrical pulses which the auditory nerve needs. The nerve cannot send sound information to the brain. A problem in the inner ear can cause a sensorineural hearing loss. This can be mild, moderate, severe, profound or even total hearing loss. Sensorineural losses are usually permanent. There is no surgical procedure to cure problems in this part of the ear; depending on the cause, medication may be helpful in some cases. Conventional hearing aids can usually help in mild to severe hearing loss. Cochlear implants can be a very effective option for those with severe, profound or total hearing loss, meaning those people who are not able to gain sufficient speech information even with the most powerful hearing aids.

Neural Hearing

Neural hearing loss is due to a problem in the nerve pathway...
the auditory nerve being damaged or missing so that signals cannot pass to the brain. In very rare cases hearing loss may be caused by the absence of or damage to the auditory nerve, resulting in a neural hearing loss. Conventional hearing aids will give little benefit because the nerve is not able to pass on enough information to the brain. A cochlear implant will not help unless there is some auditory nerve function.

Conductive Hearing

Conductive hearing loss is due to a problem in the outer...
or middle ear blocking the sound, making it harder to hear. Eardrum and bones cannot vibrate. Any problem in the outer or middle ear can block sound to the ear and cause a conductive hearing loss (so called as it stops the ear from conducting sound properly). Conductive losses are usually mild or moderate in nature, i.e. causing hearing loss of up to about 60 or 70 decibels. Conductive hearing losses can be temporary in some cases. In many cases medication or surgery can help, depending on the cause of the problem. Hearing loss does not only mean the inability to hear loudly enough. Some people may have great difficulty in hearing within a specific and narrow frequency region. This may result in a “discrimination loss,” whereby one can hear speech but not understand speech. If not detected and treated in time, hearing loss in a child can have a very adverse effect on the child’s language development and learning ability. With children as well as adults, untreated hearing loss can have broad-reaching affects. Hearing problems often make it difficult to “keep up,” which can lead to a sense of isolation, fatigue and loneliness. As hearing is often associated with old age – and frequently interpreted as a lack of intelligence – it may affect life at school and work, as well as social interaction and general quality of life. It is therefore important to do something about hearing problems as soon as possible.

Treating Hearing Loss

Conductive hearing losses can sometimes be helped through surgical...
or medical treatment. In most cases, however, hearing aids are the only means of helping hearing loss. This is especially true with sensorineural hearing losses. There is a wide variety of hearing aids available today in which sound reproduction can be tailored to the user’s own unique hearing loss and needs. It is important to note that, while hearing aids may not restore normal hearing, they can significantly improve hearing ability in all situations – allowing for a fuller life in many ways. For further information on hearing aids, please click here.