Sound absorption coefficient

Determine the sound absorption coefficient of your materials thanks to the expertise of CEVAA. Improve the acoustic comfort and sound quality of your product or your premises.

Acoustic waves absorption

Sound waves are not always completely reflected by obstacles. Depending on the frequency of the incident wave and the characteristics of the materials, the obstacles absorb a greater or lesser quantity of energy.

By choosing materials according to their absorption coefficient, it is possible to correct the acoustic behavior of a room, an enclosure or even a vehicle passenger compartment.

The thickness of the material also plays an essential role: while a light veil is generally sufficient to absorb the high-pitched extremes and prevent them from being reflected, several meters of thickness may be necessary to absorb signals with frequencies below 50 Hz.

The absorption coefficient α of a material is the ratio:

α is a dimensionless number. It depends on the nature of the material and the frequency of the incident wave on the wall.

– If α is equal to 1, this means that the wall has absorbed all the energy and nothing is reflected: the material is absorbent.

– If α is equal to 0, this means that the wall has reflected all the energy and nothing is absorbed: the material is reverberant.

Tests and measurements on acoustic equipment

The impedance tube makes it possible to measure the absorption coefficient of a material, under normal incidence, in a simple, fast and perfectly reproducible way. Additionally, testing procedures meet ISO-10534 and ASTM E-1050-98 standards. The CEVAA has tubes with an internal diameter of 29 mm, 44 mm and 100 mm. They cover a wide band of frequencies between 50 and 6300 Hz.

The CEVAA also has an Alpha Cabin with a volume of 6.44 m3. It thus performs measurements of the acoustic absorption coefficient in diffuse fields.