Air-coupled ultrasonic spectroscopy for the study of membrane filters

This work presents an investigation carried out to apply a broadband ultrasonic spectroscopy technique to the study of membrane filters. The technique is based on the analysis of the amplitude spectra of broadband airborne ultrasonic pulses transmitted through filter membranes. In particular, analysis of the through thickness resonances is used. Density of the membrane and velocity and attenuation of sound waves are obtained. These magnitudes are correlated to other properties of the membrane like porosity, pore size, water flow and bubble point. Observed relations suggest that this technique can be used as a filter integrity test and as a non-invasive characterization procedure.