Equivalent surface area of the sound-absorbing tested sample, acoustic absorption of the sample (A)

Professional Definition

The equivalent sound-absorbing surface area of the tested sample is a measure that indicates the sound absorption effectiveness of a particular, single object (acoustic system, furniture, person). It is the difference between the acoustic absorption of a reverberation chamber with the sample placed in it and the absorption of an empty chamber.

Unlike flat materials (where we use the coefficient α), here the result is a specific number of square meters [m²] per one object. This allows for precise acoustic design based on the number of elements (e.g., “we need 10 baffles”), rather than the surface area of the walls.

Acoustics in Simple Words

Imagine you have a bucket of water (sound) and you want to see how much water one specific sponge of an unusual shape can absorb. You do not measure the surface area of the sponge with a ruler, as it has many nooks and crannies. Instead, you drop it into the water and check how much water has reduced in the bucket. The acoustic absorption of the sample is the result of such a test – it tells us how much “acoustic water” one specific element, such as a single panel suspended from the ceiling, can absorb, regardless of its complicated shape.

Summary

This parameter is used for discrete (single) objects such as baffles, ceiling islands, or furniture. It allows engineers to precisely select the number of acoustic systems needed to achieve a specified reverberation time in a room.