Larry E. Humes
Dept. of Speech & Hear. Sci., Indiana Univ., Bloomington, IN 47405
In this presentation, some of the pioneering work performed by Harvey Fletcher and colleagues on the loudness of simple and complex sounds will be reviewed. The focus will be placed on the model and data presented by Fletcher and Munson [H. Fletcher and W. A. Munson, J. Acoust. Soc. Am. 5, 82--108 (1933)]. In this classic paper, the authors lay a solid foundation for the understanding of loudness which remains remarkably intact today in light of contemporary psychophysical and physiological knowledge. They provide thorough descriptions of several loudness phenomena, including loudness growth, monaural loudness additivity, and binaural loudness summation. Among other things, they demonstrate that loudness for a single tone grows as a function of the cube root of stimulus intensity, that loudness is additive for stimulus components in separate auditory filters or in separate ears, and that loudness of partially masked stimulus components is also additive once adjustments for partial masking have been made. Fletcher and colleagues were also interested in applying their model of loudness to hearing-impaired listeners. Their prior efforts in this area will be updated by the review of contemporary data on loudness growth and summation in the hearing impaired.