Technical Column

Setting Background Noise Levels in an Anechoic Chamber

2025年5月27日

Acoustic Power Measurement

How to Set Background Noise Levels in an Anechoic Chamber

Background noise refers to the ambient sound present when the test source is inactive—in other words, the baseline quietness of the anechoic chamber.
While this may sound straightforward, there are several important considerations when defining acceptable background noise levels.

Recommended Background Noise Thresholds

The background noise level must be significantly lower than the acoustic power level of the device under test (DUT).
A common guideline is that the background noise should be at least 10 dB lower than the minimum sound pressure level to be measured.
To enable the measurement of quieter sources, the chamber’s background noise must be proportionally lower.

Designing for Environmental Noise and Vibration

To achieve a sufficiently low background noise level, the chamber must be designed with proper sound insulation and vibration isolation, tailored to its installation environment.

Let:

  • A = Environmental noise and vibration level at the installation site
  • B = Sound insulation and vibration isolation performance of the chamber
  • C = Background noise level inside the anechoic chamber

Then:

A – B = C

In other words, the target background noise level (C) is determined by the measurement requirements.
From this, the required chamber performance (B) can be calculated based on the site conditions (A).

If the installation site is subject to high levels of ambient noise or vibration, higher-performance insulation and isolation measures will be required to meet background noise targets.

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