Acoustic Camera Systems - Buying Guide

Technical Reference

Acoustic cameras (microphone arrays with beamforming processing) create real-time visual maps of sound source distributions overlaid on a camera image. Selection criteria include: frequency range (typically 500 Hz–20 kHz for vehicle and machinery NVH), spatial resolution (related to array aperture and frequency), number of microphone channels (32–128 for automotive, 16–32 for general use), beamforming algorithm (delay-and-sum, CLEAN-SC, DAMAS), distance range, and dynamic range. The Norsonic Nor848A features 64 microphones in a 0.6 m × 0.4 m planar array achieving approximately 5° spatial resolution at 5 kHz at 1 m distance.

Beamforming Algorithm Selection

Conventional delay-and-sum (DAS) beamforming is fast but produces sidelobes that can mask weaker sources near dominant sources. CLEAN-SC (source-coherent variant) iteratively removes the contribution of identified sources, providing cleaner maps with fewer artefacts — essential for vehicle NVH work with multiple simultaneous sources. DAMAS (Deconvolution Approach for the Mapping of Acoustic Sources) provides the highest resolution but requires longer computation.

Frequency Range & Array Size

Array aperture determines the lowest usable frequency: larger arrays work at lower frequencies. A 0.6 m aperture provides useful resolution from about 500 Hz. Upper frequency is limited by inter-microphone spacing (aliasing). For automotive wind noise (100–500 Hz), large in-duct arrays are required. For machinery source identification (500 Hz–8 kHz), compact 32-element arrays suffice.

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