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An acoustic holography system creates highly accurate sound maps using measurements made at multiple points next to the object. These use a hand-held microphone array, a fixed array, or a robot-controlled microphone array. With this method, many measurement points can be acquired simultaneously – saving time compared to traditional sound intensity methods.

The resulting maps show sound levels as colours emanating from the object’s sources. These sound maps can be laid over images and videos for easy relation to the test object. The software allows any relevant property of the soundfield to be calculated, such as source strength and directivity. Conformal noise mapping options allow measurements that follow the shape of the object, and using a set of patch measurements, you can then create animated, 3D noise maps on a 3D model of the object. Users can also listen to individual points during transient events.

USE SCENARIOS

• Detailed noise mapping of vehicle components such as engines and powertrains
• Mapping overall product noise for white goods, office machinery, and heavy machinery
• Analyzing acoustic leaks in door seals
• Automated, robotic measurement processes with a limited array size
• Capturing transient noise events in detail

Brüel & Kjær’s patented holography algorithm SONAH (statistically optimized nearfield acoustic holography) improves resolution over conventional NAH (near-field acoustic holography), and allows accurate mapping of objects with smaller microphone arrays that don’t cover the whole measurement object at one time. It also allows more arrays that are not rectangular, which gives more flexible array options such as combined arrays that also allow beamforming capabilities for higher frequencies and moving sources.

CAPABILITIES

• Low to medium frequencies (100 Hz – 2kHz)
• Mapping of sound pressure, sound intensity, particle velocity and sound quality metrics
• Noise sub-source sound power contribution analysis
• Analyzing transient events, averaging in time, RPM, and angle domains
• Conformal mapping where sound maps follow the object’s shape
• Intuitive documentation including animations using source-image overlay
• Spatial transformation of sound fields (STSF)

ADDITIONAL CAPABILITIES

• With the addition of Brüel & Kjær’s wideband holography option, you can extend the frequency range limit, allowing good sound power estimates over a wide frequency range from one measurement – instead of needing a separate beamforming measurement for higher frequencies
• A proximal holography option (BZ-5963) makes conformal maps that follow the shape of the object under test, in one measurement, using our equivalent source method (ESM). As all the signals are obtained simultaneously, transient calculations can be performed to create the 3D noise map
• A robot positioning system (BZ-5370) assures test repeatability with fully automatic measurements

For more information on all of the extra options available including sound quality metrics calculations, transient measurements, panel contribution, intensity component analysis, in situ absorption, see Array acoustics options.