What Is an Acoustic Anechoic Box?
An anechoic box has two properties: sound insulation and sound absorption.
It blocks sound waves coming from outside the box, while it does not reverberate sound inside the box. It is used to measure sound waves generated by compact driving components such as motors and fans, and electrical equipment using a sound level meter or analyzer.
How to use an Acoustic Anechoic box
The acoustic anechoic box is used in combination with a sound level meter and analyzer. A microphone cable is connected to a measuring instrument installed outside the box and a microphone is set inside the box via a cable port in the anechoic box. The generated sound of a DUT (device under test) is measured by operating the measuring instrument outside the box.
Difference between an Acoustic Anechoic chamber and an Acoustic Anechoic box
Unlike an anechoic chamber, there are no requirements by ISO standards on its design and measurement, but it is used for the purpose of a simplified measurement. However, correlative and comparative measurements are feasible by making corrections based on the master data acquired in an anechoic chamber.
Technical specifications required to an Acoustic Anechoic box
The background noise inside an anechoic box should be a very quiet environment. It may be preferable for the background noise to be at least 10 dB lower than the measurement sound of DUT. In other words, when the measurement sound is 30 dB, the environment inside the anechoic box should be quieter than 20 dB. Therefore, the anechoic box is required to have high sound insulation value.
Measuring instruments used in the Acoustic Anechoic box
and reliable measuring instrument manufacturers
The measuring equipment used in combination with the anechoic box should be selected according to the sound generated by DUT, and relatively high-performance microphone and analyzer are required as well.
Reliable measuring instrument manufacturers: Hottinger Brüel & Kjær, GRAS, Siemens, Onosokki, Rion…etc.