International Noise Awareness Day

Wednesday, April 26th, 2017

EAA INAD2017 logo

 

Noisella in the Sound Space

 

What is noise ?

Noise is a sound, an unpleasant sound. Sounds are vibrations of air or solid particles from a source sound (road traffic, television, object falling on the floor...) to our ears.
The vibrations propagates from the source to the ears but the particles moves around the positions they had before the sound:

Particles vibrates around their positions (top animation) but the sound wave is propagating on larger distances (bottom animation)

How do we "feel" noise ?

Our ears are not just the visible parts everyone of us can see or touch. They includes bones, ligaments, hairs... which move in different ways depending on the sound amplitude and the sound frequencies (low frequencies: low-pitched sounds, high frequencies: high-pitched sounds).

Actual Size Of Human Ossicles On Adult Index, photo by Eric Levi Actual size of the human bones on an adult index, photo by Eric Levi

Higher frequencies produce faster vibrations of the air particles than lower frequencies.
The frequencies of the sound vibrations are detected inside our ears by small hairs. Different frequencies move different hairs. In turn, these hairs vibrations are converted in electric signals and are sent to our brain via nerves.

Audible Frequency Range The audible frequencies to humans. Turn on the volume of your computer and move your mouse over the picture to hear vibrations at a given frequency. Don't worry, the noise level send to your speakers is far from being coherent with the deciBel scale of the picture. 1 Hertz means 1 vibration per second, 10 000 Hertz means 10 000 vibrations per second.

To learn more about how we hear sounds and noise, have a look at this 7-minute video by Brandon Pletsch on Youtube.

What are the effects of noise ?

Noise is vibrations, if there is too much vibrations (too high noise amplitude) or high vibrations for a long time (like listening music at a high level for a long time), one of the organs composing the ear can stop functioning correctly, sometimes definitively.

Noise can also cause lack of sleep or stress which are terrible for the health and for the wallet. Indeed, noise and its effects imply important costs for people, institutions and countries due to the consumption of anti-stress medications, sleeping pills, specific equipments for people expose to noise at work, equipments for hearing impaired...
As an example, the cost of the noise effect in France (a country with around 70 millions inhabitants) has been estimated to more than 50 billions per year in 2016.

Noise is stress

 

How to reduce noise ?

Stoping noise is stoping vibrations and heavy elements vibrate less than light ones. One way to reduce the outdoor noise inside a house or to reduce the noise coming from another room is to use heavy walls. A wall of bricks will further reduce the sound level between two rooms than a wall with a simple plaster board. Other ways have been developed such a multiple plaster boards with porous materials between them. These "light" solutions also reduce the vibrations.

In DIY stores, look for materials or elements with high sound indexes such as αw or Rw. The higher their values, the higher the sound absorption or sound insulation.

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