Transfer function 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 Transfer function measurements: Alexander Mayer, mdw - University of Music and Performing Arts Vienna, Department of Music Acoustics – Wiener Klangstil (IWK), 18.2.2020 Transfer function from shaker to microphone 1 meter in front of the instrument. Frequency range specified in the Filename. Shaker exciting with a frequency sweep on the bass side of the bridge (shaker type: Minishaker by BNK). Pressure measurement with a ROGA RG50 microphone. Photos of the setup: Thilo Hirsch 18.2.2020 ________________________ How to read VIA-Files: Line 1 to 9: Header, Line 8 holds the number of values Data is organized as followed: 1st col: Frequency [Hz] 2nd col: Magnitude [as Factor not dB!] 3rd col: Phase [rad] 4th col: Real part [as Factor not dB!] 5th col: Imaginary part [as Factor not dB!] (so only first 3 columns are needed) To get dB Value: Amplitude[dB] = 20 log [Magnitude] Usually the Magnitude was calculated as response/reference (input) in the frequency domain. As for measuring the mechanical admittance the sensor is most likely an accelerometer (capturing the response in m/s2 of the object of interest) and the reference an impact hammer capturing the input force in Newton. As the mechanical admittance is defined as v/F (speed over force) the acceleration signal has to be integrated. The here captured signals are integrated in the frequency domain, what means the magnitude is divided by the corresponding frequency value in s-1. Values coded like: 3.30750000000000E+1 -> 3.3075 * 10 -> 33.075