 The Fletcher–Munson curves are one of many sets of equal-loudness contours for the human ear, determined experimentally by Harvey Fletcher and Wilden A. Munson, and reported in a 1933 paper entitled "Loudness, its definition, measurement and calculation" in the "Journal of the Acoustical Society of America".The first research on the topic of how the ear hears different frequencies at different levels was conducted by Fletcher and Munson in 1933.Until recently, it was common to see the term "Fletcher–Munson" used to refer to equal-loudness contours generally, even though a re-determination was carried out by Robinson and Dadson in 1956, which became the basis for an ISO 226 standard.