Loudness of Complex Sounds as a Function of the Number of Components

The loudness of complex sounds was studied as a function of the number of components. Complexes of two, three, four, and eight tones, and a band of white noise were matched in loudness to a 1500-cy tone. The over-all spacing, ΔF, between the lowest and highest components of these stimuli was held constant at either 175, 1600, or 3400 cps. All the complexes were centered around 1500 cps when ΔF was either 175 or 1600 cps. At each of the four levels tested (25, 50, 75, and 90 db SPL), loudness remained essentially unchanged when only the number of components within a complex was varied. This invariance of loudness occurs even though inhibition may be greater within the complexes that contain a larger number of components. It is suggested that the increased inhibition may be offset by greater loudness summation when the energy is more evenly distributed within the complexes.