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Standard sound power test methods have existed for numerous years to allow for appropriate noise labeling of products for validation or for monitoring of changes. More recently, advanced methods such as acoustic holography and beamforming have also been successfully used for measurement of sound power and noise source identification. Sound power is a standard requirement for off-highway and agricultural vehicles, construction and power generation equipment, refrigeration and cooling devices, and many other consumer products. In the automotive industry, the engine and a few accessories (AC compressor, power steering pump) are tested for sound power. While sound power testing methods are well known and tests are conducted in most labs by efficient and often automated test procedures, the root-causing strategy in the case of lack of compliance to a specification is still mostly based on trial-and-error.

Farfield beamforming is a powerful tool for identifying spatially distributed noise sources. The technique yields an image of the relative sound levels within the measurement aperture. The latest version of the beamforming software is now able to estimate the total power within its measurement aperture. In this work, the noise sources on three types of construction equipment are imaged with a beamforming array, while simultaneously the radiated sound powers are determined by a six-microphone hemisphere per ISO 6393 or ISO 6395. Of particular interest are: noise induced by turbulent flow at the exit of an exhaust stack, the effect of a noise reduction package in the engine compartment, and crawler track noise during motion. The absolute levels of the mapped source regions are compared with the total radiated sound power.