Posted By Adrian Watson Dear Maria, Use an Octave Band Frequency Analyser, measure the Sound Pressure Levels in each of the Octave Bands. From the sound pressure level measurements, subtract the A weighting corrections if necessary and the mean plus one standard deviation attenuation. The mean and standard deviation are given by the manufacturer of the hearing protection. Sum the resulting attenuated noise levels in all of the octave bands and you can ascertain whether the noise protection is adequate.