A device to measure or to estimate the acoustical output of the loudspeaker of a earphone, earplug, headphone or ear muff, and to measure the ambient environmental sounds where appropriate. The loudspeaker is connected to an electronic audio device. The acoustical output of the loudspeaker may be measured by means of a microphone placed in close proximity to the loudspeaker; or estimated by means of measuring the output of the audio amplifier (in the electronic audio device) and using the output/input transfer function that relates the acoustical output of the loudspeaker to the output of the audio amplifier; or estimated by means of the output the digital signal processor (in the electronic audio device) and using the output/input transfer function that relates the acoustical output of the loudspeaker to the output of the digital signal processor. The measurement or estimation of the acoustical output of the loudspeaker (and measurement of the ambient environmental noise, if appropriate) may be used to realize a noise dosimeter or as a means to determine the maximum allowable output limit of the electronic audio device.