“The properties or qualities of a room or building that determine how sound is transmitted in it.”

Sound is the oscillation of particles as energy travels through a medium such as air. These oscillations stimulate the ear which sends a signal to the brain and sound is perceived. Therefore it is important to account for the human perception of sound.

Understanding Sound


Frequency is measured in the number of particle oscillations (cycles) in one second. A healthy ear can hear sounds of very low frequency, 20 Hertz (or 20 cycles per second), to a very high frequency of 20,000 Hertz. Normal speech ranges from about 200 Hertz to 2000 Hertz (20KHz).

Energy in a sound

dB (Decibel) – This is the unit in which we measure the sound that Humans can generally hear. A person with good hearing is -5dB


Reverberation is a key characteristic of a room’s acoustic environment. It is created by sound reflecting off the walls, floor and ceiling. When too much sound bounces around a space, speech becomes hard to understand.


Sound absorbing panels and acoustic materials come in different formats to help your space have the ideal reverberation time while minimizing echoes and creating a pleasing acoustic environment.


ISO 11654:1997 Acoustics – Sound absorbers for use in buildings – Rating of sound absorption

Testing terminology – BS EN ISO 354:2003Acoustics. Measurement of sound absorption in a reverberation room

The material’s ability to absorb sound is generally presented with absorption coefficients measured in different frequencies. This means in practice that one material has a number of different absorption coefficients based on frequencies.

When specifying a suitable absorption class for each product, a product is first measured according to EN ISO 354. The result from this test is an absorption curve, which declares absorption coefficients for each frequency used in the test.

Αw Sound Absorption Class
1.00-0.95-0.90 A
0.85-0.80 B
0.75-0.70-0.65-0.60 C
0.55-0.50-0.45-0.35-0.30 D
0.25-0.20-0.15 E
0.10-0.05-0.00 Not Classified