How we hear

To understand the various causes of hearing loss and how the many features of Siemens hearing systems can help restore hearing, it is important to understand how the ear and the brain work together to enable us to hear.

How we hear

To understand hearing loss, it helps to understand how we hear. Your ear is an amazing organ that, very simply put, turns sound waves in the air into information in your brain — and sometimes emotions in your heart.

It can perceive sounds from barely audible to very loud, differentiate their loudness and distance, and pinpoint the direction of a sound source to an amazing degree of accuracy. The short movie on the following page will clearly demonstrate how your ear.

The ear

The human ear consists of three parts- the outer, middle, and inner ear.

ear and hearing

(pic: Ear and Hearing)

The outer ear:

consists of the visible part of the ear, also called the auricle, and the ear canal. What we call ‘noises’ are actually just ‘sound waves’, which are transmitted by the air. Sound waves are collected and guided through the ear canal to the eardrum. The eardrum is a flexible, circular membrane that vibrates when sound waves strike it.

The middle ear:

is an air-filled space separated from the outer ear by the eardrum, or the tympanic (pronounced: tim-`pa-nik) membrane. In the middle ear are three tiny bones: malleus, incus, and stapes, often referred to as the hammer, the anvil, and the stirrup. They are collectively known as the ossicles. These form a bridge from the eardrum to the inner ear. The ossicles also vibrate in response to movements of the eardrum and in doing so, amplify and relay the sound to the inner ear via the oval window.

The inner ear:

referred to as the cochlea (pronounced: kohk-le-a), is similar in shape to a snail shell. It contains several membranous sections filled with fluids. When the ossicles conduct sound to the oval window, the fluid begins to move, thus stimulating the minute hearing nerve cells, called hair cells, inside the cochlea. These hair cells in turn send electrical impulses via the auditory nerve to the brain where it will be interpreted as sound.

Loudness

The loudness of sound is measured in units called decibels, abbreviated “dB”. A decibel unit expresses the relative intensity of sounds on a scale from zero for the average least perceptible sound to about 100 dB, which is near the level most people find uncomfortably loud. Normal speech is around 50 to 60 dB. The following chart demonstrates the sound scale in decibels.

When an individual is over-exposed to excessive loudness, sensitive structures of the inner ear, such as hair cells, can be damaged, causing noise-induced hearing loss (NIHL).