A computer implemented method, or hardware filtration apparatus, and computer usable program code for measuring porosity in materials. An ultrasonic signal is emitted from a transmitting transducer in an ultrasonic measurement system into a material. A response signal is received at a receiving transducer in the ultrasonic measurement system from the material. The response signal is filtered to pass only frequencies in the response signal within a selected frequency range to form a filtered response signal. A porosity level of the material is identified using the filtered response signal.