Hearing Protector Attenuation Measurement by Bone Conduction Loudness Balance Compared with Real Ear Attenuation at Threshold in a Sound Field

Abstract A new method designed for the measurement of hearing protective device noise attenuation under actual use conditions was compared with the standard method, real ear attenuation at threshold as specified by American National Standards Institute Standard S12.6-1984. The procedure, bone conduction loudness balance, utilized pulsed sounds delivered alternately by a bone conduction vibrator on the forehead of the hearing protector wearer and by a loudspeaker outside the hearing protector. The bone conduction sound was maintained at a constant level and frequency and the air conduction sounds (1/3 octave bands of noise from 125 to 8000 Hz) were varied in level by the hearing protector wearer to achieve a subjective impression of equal loudness between the bone-conducted and air-conducted sound pulses. The difference in level between the sounds required to balance with the hearing protector on or off was defined as the attenuation. The loudness balance procedure was evaluated for three different backgro...