Abstract
To improve the search functionality of online sound effect libraries, timbral information could be extracted using perceptual models, and added as metadata, allowing users to filter results by timbral characteristics. This paper identifies the timbral attributes that end-users commonly search for, to indicate the attributes that might usefully be modelled for automatic metadata generation. A literature review revealed 1187 descriptors that were subsequently reduced to a hierarchy of 145 timbral attributes. This hierarchy covered the timbral characteristics of source types and modifiers including musical instruments, speech, environmental sounds, and sound recording and reproduction systems. A part-manual, part-automated comparison between the hierarchy and a freesound.org search history indicated that the timbral attributes hardness, depth, and brightness occur in searches most frequently.