Laser interferometry measurements of a Moroccan rabāb

Instrument: rabāb Country of origin: Morocco Place of origin: Fès Instrument maker: Abdessalam Chiki Year of manufacture: 2015 Location: Basel, private property of Thilo Hirsch
Dimensions: Total length: 513.2 mm Max. Body width: 114.8 mm Width at the upper end of the skin: 96.2 mm Width at top nut: 31.6 mm Body depth at the upper end of the skin: approx. 80 mm
Vibrating string lengths: d-string: 410 mm G-string: 403 mm
Materials: Body: walnut Pegbox: walnut Fingerboard: Acajou (mahogany) Decoration: mother-of-pearl Bars: spruce Top nut, tailpiece button: Bone Bridge: bamboo Top: goatskin
Laser interferometry measurements: Alexander Mayer, mdw - University of Music and Performing Arts Vienna, Department of Music Acoustics – Wiener Klangstil (IWK), 18.2.2020
Each figure (Filenames: A_####Hz.jpg) corresponds to the frequency of excitation on the bass side of the bridge (shaker: Frederiksen Vibration Generator Nr 2185.00). Images are made by time-averaging of laser speckle interference at the camera (time-average ESPI approach). Operating deflection shapes (roughly translating to theoretical vibrating modes) are observed at each frequency.
Photo of the setup: Thilo Hirsch