Sound absorption

Sound absorption: the cure for annoying reverberation

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Reverberation results in poor acoustics, poor speech intelligibility and more noise pollution.

Sound absorption is the conversion of sound energy into heat. The sound disappears into the material. The sound waves deform the material, which costs energy. Depending on the type of material, the energy will partly be returned as reflected sound. Each material has absorbency. Even hard materials such as concrete, glass and laminate absorb noise.

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Absorbency

To properly know the absorbency of a material, the manufacturer or supplier must have an acoustic product tested by an independent institute. This happens in a reverb room. In short, this is where they test: in a room with lots of hard surfaces and a lot of reverb, which influences the reverberation in the room.

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European ISO 11654 Standard Guidelines

The most used term in the Netherlands is the αw and is determined in accordance with the guidelines of the European ISO 11654 standard. This value is determined by determining a weighted average of the frequencies 250, 500, 1000, 2000 and 4000hz. The αw value is expressed as a number between 0 and 1. 0 means no absorption and 1 means 100% absorption. For the most part, the sound that we produce with our voice is between 250 and 4000hz. Actually, the αw value is therefore a single-digit value that focuses primarily on speech and the average human voice. Although our vocal range is on average between 250 and 4000 Hz, our hearing has a range of approximately 20 to 20,000 Hz.

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