A new ultrasonic technique for studying dewetting and cumulative internal damage in filled polymers such as solid rocket propellants has been developed. The ultrasonic measurements correlate well with volume‐dilatation data in tension. Ultrasonic assessment of damage has also been performed for uniaxial compression and shear strain fields. Experimental results show that for a filled polymer a universal relation exists between acoustic measures of damage and the maximum principal strain for fairly general states of strain. A quantitative physical model relating the observed ultrasonic effects to specific damage events is presented. Estimates of the vacuole size and number density, arising from dewetting, obtained by applying this model to experimental data are in excellent agreement with independent microscopic observations. Time‐dependent void growth at constant strain has also been monitored by means of the ultrasonic technique.