Brüel & Kjær Sound & Vibration Measurement A/S

Noise monitoring solutions for noise source identification - Monitoring and Testing

Before you can determine what design changes are appropriate to reduce the noise emitted by a product, you need to be able to characterise it in terms of: Spectral content: The location of the dominant sources. The relative importance of dominant sources. Noise Source Identification employs a number of tools to perform such a characterisation.

'Hotspot' Search

Using on-line intensity measurement, the main sources can be located by moving the intensity probe across the surface of the object. This method is quite good for getting an overview; however it does not quantify the 'hotspots' and it does not document its results very well.


Intensity maps can be used to identify the location of noise emission 'hotspots' by documenting what parts of an object radiate and at what level. Combining mapping with spectral analysis allows this to be done for a specific frequency band, for example, when looking for annoying pure tone components.


Based on the map's sound power, radiation may be determined for the whole object, for particular substructures or for individual 'hotspots'. Ranking these will help to determine the relative contribution of substructures and 'hotspots' to the overall sound radiation of the full object. Thus identifying where a change can have the greatest effect.

Advanced methods

Unlike direct intensity measurement, advanced methods like STSF allow the intensity level to be determined close to the surface of the object giving higher resolution and more reliable results. Non-stationary STSF even allows analysis to be performed as a function of time to determine the dynamic noise radiation, also of transient sources.