The sound absorption rate of a single sound-absorbing wedge in an Anechoic chamber

We received the following inquiry from a North American distributor.

They are asking about absorption ratio and absorber coefficient of wedge you quoted 0.6mtr2

This is a question from a user who is considering the installation of an anechoic chamber overseas. We were proposing a chamber with 600mm thick wedges as the inner wall sound-absorbing layer.

However, this question is somewhat meaningless. The reason is that the sound absorption performance of the anechoic chamber as a room is not calculated or designed based solely on the sound absorption performance of the individual sound- absorbing wedges.

The sound absorption rate of the sound-absorbing wedge is measured using the normal incidence method (ISO 10532-2 Acoustics – Measurement of sound absorption and impedance by the impedance tube – Standing wave ratio method), but the sound absorption design of the anechoic chamber is not determined solely by the absorption rate.

There are formulas available to estimate the sound absorption performance of an anechoic chamber based on the absorption rate, but we are not using them at the moment.

https://anechoic-room.com/techint/iso37452012/
Reality v.s. Ideal in Anechoic Chamber Design Based on ISO 3745:2012

As mentioned in this article, the 2012 revision of ISO 3746 removed the following statement that was previously included: The sound-absorbing materials applied to the walls and ceiling of the anechoic chamber should have a normal incidence sound absorption coefficient of 0.99 or higher at the target frequency.

In other words, the anechoic chamber only needs to satisfy the inverse square law as a room. The reason for this change is that, due to improvements in the sound-absorbing materials, chamber shapes, and other factors, the sound absorption performance of anechoic chambers has been steadily increasing, making the traditional model cases no longer applicable.

In other words, the design methods for anechoic chambers vary between manufacturers, so it is not simply a matter of using sound-absorbing wedges with a high absorption rate.

Naturally, the details of the design methods are company secrets, so we are unable to provide an answer. The same applies to other manufacturers. Instead of proving specific details, we offer performance guarantees.

We communicated these reasons to the agency at the beginning and got them to understand and agree.