Rhona P. Hellman
Aud. Percept. Lab., Northeastern Univ., 360 Huntington Ave., Boston, MA 02115
More than 70 years ago, Fletcher and his colleagues at Bell Telephone Laboratories initiated the first comprehensive investigations of loudness. Fletcher recognized that to improve the quality and efficiency of speech communication systems, one must know how the ultimate receiver, the human auditory system, processes and perceives sound. In his pioneering loudness studies, Fletcher devised innovative techniques for the measurement of loudness, uncovered the key parameters that modify loudness, and developed a model relating loudness to basic properties of the hearing mechanism. The achievements of Fletcher and his group demonstrated that loudness measurements can disclose (1) the relation between the spectral selectivity of hearing and sound intensity, (2) the effects of masking on loudness, (3) the principles of loudness additivity, (4) the dependence of loudness on spectral bandwidth, as well as (5) the functional integrity of the auditory system. These seminal discoveries not only inspired subsequent loudness studies, they also provided the empirical and theoretical foundation of contemporary loudness research and models. [Work supported in part by NIH Grant RO1 DC00084-18.]