Abstract: A method and apparatus for checking a heterogeneous transformation process of diffusion kinetics taking in a turbulent flow of a liquid, whereby the real-time checking or control of the processes is possible. The method involves the steps of detecting acoustic vibrations caused by oscillations of bubbles present in the turbulent flow of liquid, producing an electric signal reflecting the spectral compostion of the detected signal, and forming therefrom a measure signal reflecting the relative instantaneous value of the turbulent diffusion coefficient of the flowing liquid. The apparatus comprises a series circuit including an acoustic sensing unit 1, an amplifier 2, signal processing means 3 and computing means 4, wherein the signal processing means 3 are equipped with a circuit for dividing the output signal of the amplifier 2 into spectral ranges and determining a characteristic value and the average value for each range and the ratio of the characteristic values.