Measurement of auditory distortion with relation between harmonic distortion and human auditory sensation

It is argued that total harmonic distortion (THD), which is commonly used to evaluate the sound quality of a sound system, does not correspond to real auditory sensation. The author discusses two studies: (1) experiments that yielded a set of curves which represent the threshold of the human ear to various orders of harmonic distortion, and (2) electronic equipment with special weighting networks that are designed according to the curves for measuring the distortion of a sound system. The measured data is dubbed the `auditory distortion figure´ and reflects the real sensation of the human ear that responds to the harmonic distortion.