Abstract: At the option of an operator, the attack or release time of a hearing aid is automatically measured, and the measurement displayed in milliseconds on a digital readout. A test tone signal of constant frequency is successively cycled between relatively low and high power levels. During the first cycle of the test signal a sample is taken and stored which is representative of the steady state response of the hearing aid under test; and during the second cycle a measurement is automatically made of the time required for the output of the hearing aid to settle to within a predetermined recovery range about the stored sample signal.