Abstract: Method and apparatus for testing leak integrity of a workpiece such as a wheel rim in which the rim is positioned within an air-tight housing with the axial rim edges is sealing engagement with opposed wall portions of the housing so as to form first and second chambers within the housing internally and externally of the rim. One of such chambers is supplied with air under pressure. Microphones are positioned in the other chamber for detecting leakage of air through the rim as a function of intensity of ultrasonic radiation emitted thereby. The test apparatus is calibrated to detect air leakage that exceeds a pre-specified maximum allowable air flow rate by removably mounting a calibration orifice on a test workpiece, with the orifice being sized to provide the pre-specified maximum allowable leakage flow rate for a satisfactory workpiece at the operating pressure of the apparatus.