Many people search the internet for earplugs which ear plugs block sound completely. Do these exist? In a word no. And they never will. The reason for this is something called bone conduction. Even if the plugs did stop all sound travelling down the ear canals some is still transmitted to the eardrum via the bones of the skull.

Sound is sensed by the eardrum which vibrates in response to the energy waves. Most of the sound which reaches the eardrum has travelled down the ear canal but some of it has been transmitted through the bone. The eardrum is tightly attached to the bone of the canal in the ear canal.

This is why people who are doing very noisy activities wear over-the-ear ear defenders. If you have ever seen anybody operating a pneumatic drill or landing an aeroplane they will be wearing these. This is because they defend the bone around the ear. They will also be wearing a tight fitting pair of earplugs underneath the ear defenders. Even these do not block sound completely but they can reduce it to a safe level.

These people in very noisy environments are defending themselves against noise-induced hearing loss. This is deafness associated with tinnitus. It is the major preventable cause of deafness. It has become a lot less common since the advent of health and safety at work. Unfortunately it is becoming more common in young people due to increased use of earphones and MP3 players.

Dr Toby Bateson for zenplugs.com

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