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An analysis of the resonant vibration of an O’Meachair cedar and mahogany Irish folk harp is reported. A report is also made of a small number of measurements carried out on an O’Meachair spruce and maple Irish folk harp. The structure and operation of the harp is described.
The theory of small vibrations of plates and wooden boards is set out.
The system devised to measure input admittance at driving points on the harp body over a frequency range O-2 kHz is described. Tests of its linearity and out of its frequency flatness are reported.
Resonant vibrations of an isolated held and barred soundboard are identified over the frequency range 0 – 1 kHz by input admittance and phase measurement. Using the Chladni powder pattern method, modal shapes on the soundboard are identified and resonant modes of vibration are classified in accordance with Richardson’s notation. Plots of input admittance versus position along the length of the soundboard are presented for each resonant frequency. Input admittance measurements across the soundboard, as part of the determination of modal classification, are also reported.
Input admittance on the soundboard of the O’Meachair cedar and mahogany Irish folk harp are reported. A plot of admittance versus frequency at string point G3 over the frequency range 0 - 2 kHz is presented as a suitable representation of the characteristic admittance profile of the instrument. Resonant vibrations of the harp are identified over the frequency range 0 – 2 kHz. At each resonant frequency from 0 – 1 kHz, plots of input admittance along the length of the soundboard are presented. Modal classifications are suggested with the assistance of input admittance measurement at positions of the central bars. Two resonant modes, which are not soundboard modes, are investigated and tentatively identified. Effective modal masses and string tensions are determined.
Based on a small number of measurements, the low frequency resonant modes of an O’Meachair spruce and maple Irish folk harp are tentatively identified by comparison with the admittance profile of the cedar and mahogany harp.
Suggestions are made for further work, with a view to apply scientific methods to the construction of Irish folk harps.
Healy, P. (1993). Resonant vibrations of the Irish Folk Harp. Masters Thesis. University of Dublin. doi :10.21427/0gye-s448