Abstract
It is assumed in the paper that the signals in the enclosure in a
transient period are similar to a noise induced by vehicles, tracks, cars,
etc. passing by. The components of such signals usually points out
specific dynamic processes running during the observation or measurements.
In order to choose the best method of analysis of these phenomena, an
acoustic field in a closed space with a sound source inside is created.
Acoustic modes of this space influence the sound field. Analytically, the
modal analyses describe the above mentioned phenomena. The experimental
measurements were conducted in the room that might comprise the closed
space with known boundary conditions and the sound source Brüel & Kjær
Omni-directional type 4292 inside. To record sound signals before the
field's steady state was reached, the microphone type 4349 and the
4-channel frontend 3590 had been used. The obtained signals have been
analysed by using two approaches, i.e. Fourier and the wavelet analysis,
with the emphasis on their efficiency and the capability to recognise
important details of the signal. The results obtained for the enclosure
might lead to the formulation of a methodology for an extended
investigation of a rail track or vehicles dynamics.
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