Abstract: A portable device primarily for use in determining the effectiveness of various personal hearing protectors in attenuating hazardous noise. The device comprises an electronic circuit for generating audio test signals at varying amplitude levels, and a display for providing numerical indications usable to measure accurately the difference in amplitudes between the respective audio signals. The test signal increases or decreases in loudness in response to a subject-operated hand switch which also triggers display of the appropriate numerical indication at amplitude levels determined subjectively by the individual being tested. The electronic circuit of the device preferably is capable of producing such test signals in complex, multifrequency form with preweighting of the power spectrum of the signal so as to emphasize the most potentially hazardous frequencies.