Noise source identification has been a subject well studied in
the past few years. Automobile manufactures along with specialized
supplies have been developed some methods in this matter. The
importance of such subject is quite obvious, especially in the auto
industry: identify potential problems and point out solutions for
NVH.
There are several methods of noise source identification widely
used. Among them, one can mention "Hotspot Search," which
consists of noise intensity measurement, mapping and ranking the
relative contribution of each substructure of one body. Another
method used, one can point out is the STSF (Spatial Transformation
of Sound Fields). It consists of a measurement over a scan plane
using a set of microphone array. In this way, a 2D sound field can
be transformed in a 3D description and source direction can be
identified.
However, when noise and vibration sources need to be identified
together in a multi-body system, conventional techniques might not
be the best choice. In this scenario, a signal phase analysis was
developed in order to cope with a low frequency noise identified in
a vehicle. The noise occurrence was measured and identified in
terms of frequency. The measurement setup was described using
accelerometers and microphones installed in the vehicle
suspension.
The vibration path was determined using bode diagrams, as long
with the noise source. The delay among signal is easy to obtain and
gives a clear picture of the vibration/noise phenomena. The
condition in which the vibration was excited was also possible to
be identified through the comparison of bode diagrams during the
noise. The method helped to identify a resonance frequency of the
brake caliper coupled with brake pads, generating a self-excited
non-linear phenomenon.
Phase analysis method has shown to be suitable not only for
noise but also for vibration. As it is simple to be applied and
also competitive cost wise in comparison with other methods, it
represents a powerful tool in noise analysis.