Technical Column
Mapping the Directionality of Acoustic Devices — Directivity Measurement with HBK Microphones, Turntable, and AEB —
Sep 5, 2025
- HBK × SONORA Acoustic Measurement Solution Official Website
- Technical Column
- Mapping the Directionality of Acoustic Devices — Directivity Measurement with HBK Microphones, Turntable, and AEB —
Simplified Performance Testing Using Anechoic Box + Sound Level Meter
Introduction: What Is “Directivity” in a Speaker?
Not all sounds radiate evenly in all directions.
Speakers, buzzers, microphones, and ultrasonic emitters often exhibit direction-dependent output levels, especially at mid to high frequencies.
Understanding their acoustic directivity is crucial for:
- Optimizing orientation in real-world installations (e.g. automotive, public address)
- Reducing unwanted noise exposure to neighboring systems
- Enhancing clarity and intelligibility in directional communication devices
Measurement Challenges: Precision and Acoustic Control Required
Evaluating directivity demands:
- A reflection-free space to avoid environmental bias
- Controlled rotation of the DUT (Device Under Test) or microphone
- Fine angular resolution across relevant frequency ranges
Combining a compact Anechoic Box (AEB) with an automated turntable and HBK microphones provides a practical and accurate solution.
Example Setup: AEB × Turntable × HBK Measurement Chain
| Component | Function |
|---|---|
| Acoustic Environment | AEB: Compact anechoic box isolating free-field acoustic behavior |
| Rotating Platform | Electric turntable with programmable angle steps and speed |
| Microphone System | HBK Free-Field Mic + LAN-XI module |
| Software | BK Connect: Real-time polar plotting and frequency-band analysis |
Types of Analysis and Output
- Polar plots (SPL vs angle) by frequency band
- Beamwidth and directivity index calculations
- Comparison of patterns across different designs or production batches
- Asymmetry or lobing detection
Ideal Test Targets
- Directional speakers, wearable speakers, soundbars
- Voice guidance devices and alerting units
- Ultrasonic transducers and beamforming elements
- Microphones and communication headsets with pickup pattern tuning
Why AEB + HBK Is a Winning Combination
- AEB eliminates internal reflections for true free-field testing
- HBK microphones ensure calibrated, broadband response
- BK Connect synchronizes rotation angles with real-time acoustic capture
- Compact, repeatable, and scalable setup for lab or QA use
Customization & Consultation
- AEB design tailored to DUT size and accessibility
- Turntable selection based on angular resolution and load capacity
- DUT fixture design and microphone positioning tools
- Support for test standard compliance or custom reporting
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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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