When a sound is made, for instance when hands clap together, when a hammer strikes a nail or when a song is sung, it causes the surrounding air to vibrate in waves rather like ripples in water. Thee waves are guided into the ear canal beginning with the outer ear and then travelling into the inner ear. The sound waves then strike the eardrum. The eardrum (as its name suggests) acts exactly like a drum; it is a taut piece of skin that vibrates in accordance with the sound waves that strike it. This then transmits the vibrations through a series of ossicles, which are the three small bones that are connected and transmit sound waves to the inner ear. The sound waves then pass through a fluid contained in a vessel that is shaped much like a snail's shell and is called the cochlea. The walls of the cochlea are covered in tiny, delicate hairs that convert the vibrations into electrical signals and send them to the brain.



The hairs are crucial to our hearing and if they are damaged will not regenerate, causing hearing damage and ultimately hearing loss.

Sound is measured according to the amount of pressure it exerts on the eardrum, known as decibels. The potential for a sound to be damaging not only depends on decibels, but also on the pitch, frequency and duration of the exposure to the sound. Noises in excess of 85 decibels can cause hearing damage and sound in excess of 120 decibels can cause hearing loss if the exposure is long enough. It is possible to recover hearing after a short exposure to high decibels; many people have experienced a ringing in the ears after attending a rock concert or spending a length of time in a nightclub. However, within 24-48 hours the ringing has subsided and hearing levels have returned to normal.

Within certain professional environments excess noise is one of the hazards of the job; machine operators, those in the music industry and airport staff are just some of those for whom constant exposure to loud noise could risk their hearing if the appropriate steps are not taken.

The most widely used protection aids in environments such as these are earplugs. Earplugs form a physical barrier between the source of the sound and the delicate apparatus of the inner ear. They offer a dampening effect, reducing the air pressure that is exerted on the eardrum thus minimising the effects of prolonged exposure to high decibels.

There are many types of earplug available with the capacity to reduce decibels by a set level. In some industries the ability to hear sound clearly is vital. Those who work in the music industry use earplugs that have a central diaphragm, allowing all frequencies of music to be reduced but still retaining an essential clarity.

If you work in an environment where sound levels are in excess of 85 decibels, either constantly or sporadically, it may well be worth investing in a pair of earplugs. Modern techniques mean that they are comfortable, practical and in some cases even fashionable.