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The best acoustic imaging results are achieved by combining Beamforming and Acoustic Holography. In brief, the relative strengths are:
Beam Forming Acoustic Holography
Quick Look
Global view
High Frequency
Airborne noise
Trial and error
Detailed Look
Local view
Low Frequency
Structure borne noise
Understanding vibration and noise

Strengths and limits of Beamforming

Strengths Limits

Setup, testing, and processing for results is very fast and simple

Quick trial and error tests

Ideal for isolated sources in space or isolated signals in time

No limit on size and aspect ratio of an object

Best tool for identifying high frequency airborne sounds (above 800Hz, above 400Hz for large arrays)

Spatial resolution no better than one wavelength

Only displays pressure at the surface of the array

Difficult to correlate with modeling tools

Cannot visualize structure modes

Dynamic range is limited to 8 to 14dB (dependent on array) in displaying results

   

Strengths and limits of Acoustic Holography

Strengths Limits

Reconstructs the complete acoustic field on the source surface: pressure, velocity, intensity and sound power

Provides high spatial resolution even for lower frequencies, and high dynamic range

Best method to identify Structure-borne sounds regardless of the frequency of interest

Allows for Panel Contribution analysis

Allows correlation with other analytical modeling tools (such as SEA, FEA etc)

Requires conformal measurement

Requires coordinates for microphones and object surface

Limited to 4 to 1 aspect ratio and nothing smaller than 150 cm2

Sensitive to high surface temperature due to working temperature range of microphones

Sensitive to high air flows around the array microphones