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VibraTec has extensive expertise in acoustic measurements, necessary to perform complete diagnosis campaigns on products or installations in order to identify root causes and propose mitigation actions.
VibraTec is able to mobilize vibration experts on short notice to go on-site (worldwide) with all necessary measurement equipment.
A major challenge to acoustic measurements is background noise, and more specifically the ability to overcome it. VibraTec can do so by using different types of measurements according to each situation’s specific needs, requirements, result format or standards.
Acoustic measurements using a sonometer or a microphone are the most common and easiest to perform. They measure acoustic pressure (SPL: Sound Pressure Level). The SPL is measured at 1 meter from the equipment or machine. These sound level measurements are rapid and provide a value in decibels (dB) that can be compared to criteria from standards or customer specifications.
The disadvantage of acoustic pressure measurements is the background noise – a key element for industrial applications. Indeed, background noise is also measured, be it from parasite noise, reflections off walls, etc; this increases the measured sound pressure and makes it more complicated to accurately define the source’s sound level.
Good preparation of the test environment can attenuate the background noise, but to obtain the acoustic characterization of only the product, other methods, such as intensimetric acoustic measurements or acoustic measurements with an array prove to be more efficient. It is also possible to use VibraTec’s anechoic chamber to controlbackground & reverberation noise.
Acoustic measurements using intensimetry are performed with an intensimetric captor composed of 2 paired microphones. They measure acoustic power (SWL: Sound poWer Level).
Intensimetry measurements use a scanning method where the acoustic intensity comes from each side of a parallepiped encompassing the product or machine that is being evaluated. This noise measurement technique provides data that is not impacted by background noise (neighboring machines in the test area): the 2 microphones are able to determine that the sound comes from in front or behind them.
Nonetheless, it remains important to reduce acoustic perturbations as much as possible to come as close as possible to free-field conditions.VibraTec proposes parasite noise attenuation solutions before the actual testing, according to the test area/bench. It is also possible to use VibraTec’ssemi-anechoic chamber to control background & reverberation noise.
The product’s global acoustic power will be determined based on the contributions of each side, presented in octave band or in 1/3-octave band. It is also possible to computea weighted decibel level for a given frequency range. The acoustic powerlevels can be compared to criteria from specifications or standards.
The ISO 9614-2 standard details the acoustic power level characterization method using intensimetry measurements. If there is little or no background noise, the sound power levels can be estimated from sound pressure measurements (sonometer acoustic measurements) based on standards ISO 3741, ISO 3743, ISO 3744, ISO 3745 and ISO 3746.
Contact us for more information regarding acoustic or noise measurements, or to discuss a specific problem.
For acoustic measurements requiring high precision, or in complex environments, VibraTec can benefit from the expertise and products produced by MicrodB. A product line of various arrays makes it possible to adapt to all cases and perform highly technical acoustic measurements. These measurements make it possible to rapidly identify acoustic sources, superposing a noise map and photos of the structure.
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