Flow over an isolated shallow open-type rectangular cavity was investigated experimentally. Pressure measurements at Mach numbers 0.3,
0.5 and 0.6 were performed. Turbulent boundary layer was naturally
developed along a flat plate upstream the cavity. During the experiments
two test configurations were employed. Strong resonance was observed in
the pressure signals obtained at M = 0.5 and M = 0.6 for the test
configuration with the short upstream plate. Instantaneous oscillating
characteristics were studied by Wavelet and Hilbert-Huang transforms of
pressure signals. The resonant intermittency was observed for a shallow
cavity flow.