Cultural Heritage Applications: Archaeological Ceramics and Building Restoration - On Statistical Pattern Recognition in Independent Component Analysis Mixture Modelling - page 146

Digital data transmission
(USB bus)

Data acquisition
setup
(RS232 bus)

Data acquisition
equipment

Analog data
transmission
(coaxial cable,
BNC connector)

CONTROL

Ultrasound
equipment

Storage box:
cables, sensors,
connectors, etc.

Mobilization

Ultrasound
transducers

Fig. 6.7 Ultrasound equipment

(a) (b)

Signal is
attenuated

Air h

Multiple reflections
are produced giving
a higher signal level

Fig. 6.8 Power signal B-Scan by non-stationary analysis a Power B-Scan b Scheme of the wall

From the spectral analysis, two frequencies (181 and 356 kHz) were found in all
the recorded signals. After estimating the B-Scan of Fig. 6.8 , the origin of the
sinusoidal frequencies was not clear enough; they could be interferences or
material resonances. Then we applied ICA to obtain more information from the
mixture matrix and recovered sources. Figure 6.9 shows the recorded signals and