Technical Column
Automated Sound Pressure Scanning for ISO 26101 Validation — Free-Field Compliance Using HBK + Traversing System in Sonora Anechoic Chambers —
2025年8月21日
- HBK × SONORA Acoustic Measurement Solution Official Website
- Technical Column
- Automated Sound Pressure Scanning for ISO 26101 Validation — Free-Field Compliance Using HBK + Traversing System in Sonora Anechoic Chambers —
Acoustic Power Measurement
Introduction: What is the Inverse Square Law in Acoustic Power Testing?
In ISO 3744 and ISO 26101, verifying that a test space approximates a free-field environment is critical.
One key requirement is confirming that sound pressure level (SPL) decreases by approximately 6 dB per doubling of distance from the source — known as the inverse square law.
To validate this, ISO 26101 specifies:
- SPL comparison at multiple distances from the sound source
- Linear decay relationship between log(distance) and SPL
- Allowable deviation within ±1.5 dB over specified frequency ranges
The Challenge: Manual Testing Is Not Enough
Accurate inverse square validation requires high-precision, repeatable measurement at defined distances.
Manual mic placement often leads to errors, variations, and low repeatability.
The solution: an automated traversing system combined with HBK’s precision acoustic front-end.
System Configuration: SPAC / VSAC × Traverser × HBK
| Component | Description |
|---|---|
| Test Space | SPAC or VSAC: Sonora’s anechoic chambers with controlled acoustic fields |
| Microphone | HBK Free-Field Mic (e.g. Type 4189) + LAN-XI modules |
| Movement | XYZ-axis traversing system (stepper motor or servo-driven, 0.5 mm precision) |
| Analysis Software | HBK PULSE or BK Connect: linear regression, deviation plots, pass/fail logic |
Why Use a Traversing System?
- Accurate mic positioning at various radii (r₁, r₂, r₃…)
- Consistent, automated measurement sweep for each frequency band
- Data visualization for inverse square plots with trendlines
- Enables ISO-compliant reporting and lab certification
Typical Use Cases
- In-house acoustic labs for small motors, fans, or appliances
- Preparing for international compliance or CE marking
- Design verification of free-field zones within custom test rooms
- Standardizing test procedures for training or production QA
Why HBK?
- High-fidelity microphones with calibration traceability
- LAN-XI modules provide synchronized, multi-channel A/D conversion
- PULSE/BK Connect offers real-time frequency analysis & ISO workflows
- Can be fully integrated with motion control and PLC systems
Consultation & Support
- Design and integration of a Sonora chamber + traversing system
- HBK sensor and software setup tailored to your test goals
- Support for ISO 26101 mic positioning and evaluation methods
- On-site training or turnkey system delivery available
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Contact Us
- Contact us by email
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- Contact us by phone
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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
Contact / Request Brochure
For inquiries or consultations regarding the total solutions provided by HBK × Sonora, please feel free to contact us using the Contact button.
If you would like a brochure sent by mail, please use the Request Brochure button.