nMeasurement
through the microphones of a dummy head
nThe headphone is connected in parallel with a second unit, being weared by the operator
nAn 1/3 octave spectrum of the equivalent level is measured at each ear for the whole exposure period
nFrom the measured spectrum it is possible to derive a correspondent far-field noise spectrum, which would create the same spectrum at the ear of the mannequin.
nThis means to remove the head-related transfer function