29 November 2010

Infrasonics: the Silent Enemy

We cannot hear infrasonic waves, as these frequencies are under that, which the human ear can pick up. Despite this, these sounds can pose a great risk to our hearing and our health.

The human ear can pick up sounds from 16-20,000 Hz. Lower sounds, in other words frequencies of 2-16 Hz, are called infrasonic. The deeper the frequency, the higher the sound has to be before we can hear it. A sound of 100 Hz needs a volume of at least 23 decibels before we can hear it. A sound of 20 Hz needs 70 decibels of volume to be heard. 4 Hz needs as many as 120 decibels before we can pick it up. In other words, we can be subjected to extremely loud noises in these frequencies without hearing it. Sounds of over 85 decibels can damage your ears and cause hearing loss.

What are the consequences of infrasonics?
Infrasonics affect our body. Sound waves, which we cannot hear, can disturb our balance nerve and cause nausea, restlessness, headaches and tinnitus. A known effect is what we call sea sickness. As well as that, infrasonics can also cause tiredness and disrupted sleep.

One reason for these symptoms is a kind of imbalance in the body. The body has its own frequencies. These typically lie between 1-6 Hz and can therefore be easily disturbed by infrasonics.

What causes infrasonics?
There are a number of natural reasons for infrasonics. It can be caused by the wind, air currents or other meteorological reasons, but machines, for example compressors or heavy vehicles, can also cause these sound waves. People who are employed in industry or people who work in large offices where there is a ventilation system are especially exposed to infrasonics.
Infrasonic waves move very slowly and have a long wavelength. They therefore only turn up in the open or in large halls and open office spaces which are longer than 20 metres.

How do you stop infrasonics?
It is difficult to stop these sound waves because of their wavelength. A door, a wall or ear plugs do not offer much protection against these sound waves. The sound waves penetrate through at almost full strength and only a certain sound-absorbing surface offers any protection against these sound waves.
Special sound-absorbing ear defenders can protect one's hearing. If they are not available, then the getting as far away from the source of the sound as possible is the best protection.

Source: Spektrum Hören Nr 3. 2010

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