A personal sound monitor wherein the sound is detected by a microphone and converted to a related electrical signal. The level of the signal is used to gate one of the plurality of levels in a scanning digital counter, the levels corresponding to various predetermined sound levels. The scanning counter controls the gating of various frequencies to an accumulating counter so that the total count is proportional to the integrated sound level to which the individual has been exposed.

A noise dosimeter having noise pick-up means for generating an analog signal in correspondence to picked-up noise, signal processing means for generating pulses in correspondence to the analog signal, and means for adding and storing the pulses.

An audio dosimeter for individual use determining exposure to sound energy as a function of both frequency and pressure level, with integration over the time of exposure and incorporating storage means preserving a quantitative measure of the exposure.

An electrical deplating read-out apparatus wherein the deplating current is preselected to give an indicated value of total deplating current in milliampere-second units.

Method and apparatus for evaluating the auditory distortion of an audio system, wherein an audio signal, whose auditory distortions are to be evaluated, is filtered by a notch filter to remove its fundamental frequency, and is then fed through a primary weighting network comprising three high pass filters followed by a secondary weighting network. The filtered, weighted signal is then amplified, recitified, further filtered, compared by taking the ratio with the magnitude of original signal and finally fed to a display unit to sow a figure that represents auditory distortion characteristics consistent with what is actually perceived by human auditory faculties.