The hydrodynamic cavitation in a Venturi tube is studied both theoretically and experimentally. A lumped parameter model was developed to describe the accumulation and dissipation of energy in the biphasic flow as a function of the bubble population characteristics (mean volume, standard deviation, and void fraction). Resistance, capacitance, inductance, and frequency lumped-parameters were identified applying the fluid conservation equations (mass and momentum) along with electrical/hydraulic analogies. Experiments with 1,2-propanediol were carried out in a hydraulic circuit composed of valves, a pump, and a Venturi nozzle. The acoustic noise generated (at different cavitation regimes) by the passage of the fluid through the tube was acquired with a piezoelectric sensor. After processing the experimental signals, the system frequency at each operation condition was determined. Plausible estimations of the void fraction were obtained at different experimental frequencies by evaluating a theoretical expression of the frequency lumped-parameter. This semi-empirical technique might be a low-cost alternative when the void fraction of a flow needs to be determined and tomography devices are not available.