Hierarchy classification:

1. top of the aat hierarchies
2. Objects Facet
3. Furnishings and Equipment (hierarchy name)
4. Sound Devices (hierarchy name)
5. sound devices (equipment)
6. [sound devices by function]
7. sound signaling devices

Anotations

Scope note:

Devices for producing sounds, consisting essentially of a disk pierced with holes arranged in a circle, rotated over a stream of compressed air, steam, or fluid, so that the stream is alternately interrupted and allowed to pass; their uses include giving signals or warnings and producing musical tones.