Spectral loudness summation: from the 60s to the present

In general, the loudness level of a broader sound is higher than that of a narrower sound centered at the same frequency, an effect commonly referred to as spectral loudness summation. From the late 1950s onwards, Scharf published several articles on this topic investigating how stimulus parameters such as the level, number and spectral separation of components of a complex tone and the spectrum shape affects the magnitude of spectral loudness summation, and how spectral loudness summation is altered in hearing-impaired listeners and under masking. In a contribution to the proceedings of the first international symposium on hearing, Scharf also provided important information of the effect of duration on spectral loudness summation, stimulating our own research in this field. This talk will provide an overview of Scharf's work on spectral loudness summation and how the view on this topic has changed over time. It will be shown that even today there are aspects of this effect that are not completely understood in the light of current loudness models.