Technical Column
How Quiet Is the Inside of an Anechoic Box?
2025年5月27日
- HBK × SONORA Acoustic Measurement Solution Official Website
- Technical Column
- How Quiet Is the Inside of an Anechoic Box?
Simplified Performance Testing Using Anechoic Box + Sound Level Meter
Simple Performance Evaluation Using an Anechoic Box and Sound Level Meter
An anechoic box is a high-performance sound-insulating enclosure designed for acoustic measurements.
It is primarily used for testing the acoustic characteristics of low-noise components, such as precision drive units.
As a general guideline, the ambient noise level in the measurement environment should be at least 10 dB lower than the sound pressure level (SPL) of the Device Under Test (DUT).
For example, to measure a 30 dB sound, the background noise should be 20 dB or lower.
In other words, the quieter the environment, the smaller the sound that can be accurately measured.
Below is the actual background noise data (A-weighted) measured inside one of our anechoic boxes:
| Frequency (Hz) | 63 | 125 | 250 | 500 | 1000 | 2000 | 4000 | 8000 | Overall (dBA) |
|---|---|---|---|---|---|---|---|---|---|
| Background Noise | -17.6 | -17.3 | -14.9 | -9.8 | -5.8 | -3.7 | -3.7 | -4.1 | 3.5 |
With a background noise level of 3.5 dB(A) inside the box, the minimum SPL that can be reliably measured would be approximately 13.5 dB(A).
To achieve such low background noise, careful selection of the installation environment is crucial.
We provide tailored solutions to meet each customer’s specific measurement needs.
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Contact Us
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Moritani Shokai
(Machinery Department No. 2, Tokyo Head Office)
Introduction of the Manufacturer
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Hottinger Bruel & Kjaer
HHBK is a merger of two companies: Brüel & Kjær of Denmark and HBM of Germany.
Brüel & Kjær is one of the world’s leading manufacturers of acoustic and vibration measurement instruments, known as a total measurement chain supplier.Learn more about HBK
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Sonora Technology Co., Ltd.
Sonora Technology is a leading Japanese manufacturer of industrial anechoic chambers and anechoic boxes.
From design and manufacturing to installation and acoustic performance assurance, Sonora provides fully integrated solutions to build complete acoustic measurement environments from the ground up.Learn more about Sonora
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