Abstract: A probe 10 and method for measuring a gaseous material, such as air, entrained in a solution (S) has a protective sheath member 14 having an ultrasonic transducer 18 encased therein and a reflecting member 42 spatially separated from the active area of face 20 of transducer 18. Upon activation of transducer 18, ultrasonic waves are emitted from transducer 18 that reflect off the gaseous material in the form of bubbles 48 and reflecting member 42 thereby producing correspondingly associated backscattered signals therefrom. Accordingly, the backscattered measurement is operative at low entrained air levels when only a few bubbles or gas 48 are present. Scattering from reflecting member 42 is useful at higher entrained air levels, approaching foam.