Phon based on newer Equal-loudness contours
ISO 226 was created by Technical Committee ISO/TC 43, Acoustics. ISO 226:2003 replaced the first edition ISO 226:1987, which has been revised technically.
The ISO 226:2003 specifies combinations of sound pressure levels and frequencies of pure continuous tones which are perceived as equally loud by human listeners.
The specifications are based on the following conditions:
• a) the sound field in the absence of the listener consists of a free progressive plane wave;
• b) the source of sound is directly in front of the listener;
• c) the sound signals are pure tones;
• d) the sound pressure level is measured at the position where the center of the listener’s head would be, but in the absence of the listener;
• e) listening is binaural;
• f) the listeners are ontologically normal persons in the age range from 18 years to 25 years inclusive.
Curves defining combinations of pure tones in terms of frequency and sound pressure level, which are perceived as equally loud. Express a fundamental property of the human auditing system and are of basic importance in the field of psychoacoustics. Combined with data on the threshold of hearing under free-field and diffuse-field listening conditions. Such equal-loudness-level contours were specified in the older version (ISO 226:1987)
During the revision of the standard, it was decided to separate threshold and supra-threshold data into two separate documents. Because the available equal-loudness-level data were not sufficient and hearing thresholds were needed.
Therefore, The threshold values were specified in ISO 389-7:1996, Acoustics — Reference zero for the calibration ofaudiometric equipment — Part 7: Reference threshold of hearing under free-field and diffuse-field listening conditions, as a part of the series of International Standards concerning reference zero values for the calibration of audiometric devices. The equal-loudness-level contours are presented in ISO 226.
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