Sound absorption

Sound absorption

The sound absorption coefficient describes the ratio of absorbed sound energy to incidence sound energy. Depending on the application, we offer the following methods for determining the sound absorption coefficient:

Measured value: Sound absorption coefficient αS for random incidence sound

Frequency range: 100 Hz...5.000 Hz (optionally 10.000 Hz)
Sample size: 10 m2...12 m2
Testing facility: Reverberation room with a volume of V = 200 m3
Testing standard: ISO 354

Measured value: Sound absorption coefficient αS for random incidence sound

Frequency range: 315 Hz...5.000 Hz (optionally 10.000 Hz)
Sample size: approx. 1 m2
Testing facility: Reverberation chamber with a volume of V = 6.35 m3
Testing standard: ISO 354 (based on)

Measured value: Sound absorption coefficient a0 for perpendicular incident sound
Frequency range: 25 Hz...6.300 Hz
Sample size: < 0,5 m2 (depending on the frequency range)
Testing facility: Various impedance tubes
Testing standard: ISO 10534-2
Measured value: Angle-dependent sound absorption coefficient αin-situ or reflection index RI
Frequency range: 100 Hz...5.000 Hz (optionally 10.000 Hz)
Sample size: 4 m x 4 m
Testing facility: In-situ or semi-anechoic half-space
Testing standard: CEN/TS 1793-5 and other methods

Reverberation room and reverberation chamber

Reverberation rooms are suitable for the measurement of sound absorption in the event of random incident sound, among other things. For standardised measurements, we have a reverberation room with a volume of V = 200 m3. Our reverberation chamber with a volume of approx. V = 6.35 is suitable for product development.

Reverberation room

We can determine the sound absorption coefficient aS according to ISO 354 in our reverberation room. False ceilings, noise protection walls, wall coverings, office furniture, and chairs for concerts and functions are typical products.

Reverberation chamber

For product development, we recommend sound absorption test in our reverberation chamber with a volume of approx. 6.35 m3. Samples with an area 1 m2 can be measured in the reverberation chamber. Based on the dimensions of the test object and the reverberation chamber, measurement results for sound absorption in the frequency range of 315...5.000 Hz can be determined. Measurements from the reverberation chamber can be converted into standardised reverberation room measurements with an accuracy of up to ± 10 %. Standardised measurements can be carried out on products in the reverberation room, once product development has been completed.

Impedance tubes

The impedance tube is used to determine the sound absorption coefficient in the event of perpendicular incident sound according to DIN EN ISO 10534-2. This measured value is of particular interest for special uses of sound absorbers and reflectors, such as for sound-absorbing road surfaces and sound-absorbing linings of anechoic rooms. In addition, impedance tube measurements are sometimes used as an orientation aid for the sound absorption expected in the event of random incident sound, as determined through measurements in the reverberation room.

In situ methods and anechoic half-space

So-called in situ methods make it possible to measure sound absorption on site, without special test facilities, or in an anechoic half-space. An in situ method for use with noise protection walls is described in CEN/TS 1793-5. Müller-BBM can use other in-situ methods as well, whereby the suitability of a method depending upon the particular application. In principle, in situ methods can be used to measure sound absorption relative to the sound incidence angle.

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