Precise and Full-range Determination of Two-dimensional Equal Loudness Contours

The equal-loudness contours describe the frequency characteristic of sensitivity of our auditory system. A set of the equal-loudness contours based on British data measured in mid-1950 was standardized as ISO 226. However, several research results reported in mid-1980 showed that the set of equal-loudness contours in ISO 226 contained a large error. We, therefore, carried out this project to determine new precise and comprehensive equal-loudness contours and to fully revise the ISO 226. New equal-loudness contours were based on the data of 12 studies, mostly from measurements by the members of this team, reported since 1983. These contours were calculated using a model based on knowledge of our auditory system. Based on the research results, draft standards of the new equal-loudness contours were made and proposed to ISO/TC 43 (Acoustics). The new standard finally was established on August 2003.