1) ISO 226: "Acoustics-Normal equal-loudness-level contours" 2003年 International Organization for Standardization
2) T. Watanabe and H. Moller: "Low frequency hearing thresholds in pressure field and in free field," Journal of Low Frequency, Noise, Vibration and Active Control, vol.9, no.3, P.106-P.115 1990
3) ISO 28961: "Acoustics -Statistical distribution of hearing thresholds of otologically normal persons in the agerange from 18 years to 25 years under free-field listening conditions" 2012年 International Organization for Standardization