Basic Facts

How we Hear

Hearing is one of our five senses and is a complex process of picking up sounds and transmitting them to the brain for interpretation. The ear is divided into three parts: the outer, middle and inner ear.

The outer ear is comprised of the pinna, the ear canal and the eardrum (tympanic membrane). Sound waves are picked up by the pinna and travel down the ear canal where they strike the eardrum. The eardrum begins to vibrate and passes the sound onto the middle ear.

The middle ear is the air-filled space behind the eardrum and contains the three smallest bones in the human body, called the ossicles. This chain of tiny bones is connected to the eardrum at one end and to the cochlea (inner ear) at the other end. Vibrations of the eardrum cause the bones to vibrate, and in turn, cause vibrations in the cochlea (inner ear). Fluid or abnormal pressure in the middle ear space restricts this process of sounds being transmitted through.

The inner ear consists of the organ of hearing (the cochlea) and also the organ of balance (semi-circular canals). As previously mentioned, the ossicles are physically connected to the cochlea. Therefore, the ossicles cause vibration of the fluid inside the cochlea. The auditory nerve is also connected to the cochlea and is ‘excited’ by fluid vibrations. The auditory nerve sends information about the sounds being heard to the auditory cortex in the brain.

How loud is too loud?

10dB - Weak Sound
30 dB - Soft whispers - Very quiet
60 dB - Normal conversation - Comfortable
70 dB - Hairdryer - Interferes with conversation
85+ dB - Vacuum cleaner, Mini-bike - Dangerous after 8 hours
91 dB - Lawnmower - Dangerous after 2 hours
100 dB - MP3s, Snowmobile, Motorcycle - Keep volume under 90dB
110 dB - Rock concert - Dangerous after 2 minutes
120 dB - Dancehalls, Power saw, Pneumatic drill - Dangerous after a few seconds
140 dB - Fired gun - Threshold of pain