PhD Thesis – An Investigation Of The Sound Production In The Turkish Musical Instrument Oud And A Proposal For Determining The Design Of Stringed Instruments From The Aspect Of Their Sound Characteristics

Abstract – The most significant factors that determine the sound characteristics of stringed instruments are their design features and material properties. However, the differences between the physical properties of the wood materials which are traditionally used in the making up of the stringed instruments, and, lack of knowledge on how the sound is handled, make the instrument design difficult in terms of sound quality. The basic aim of this study is to investigate the sound production process in the oud, and thus, to propose a research method for the design of stringed instruments in terms of their sound characteristics. Therefore, the vibration and sound features of ten ready-for-use ouds, one tanbur and one baglama were examined. One of the ouds was produced during the study for the experiments. At the first step of the study, in order to determine the sound characteristics of ouds, psychoacoustic listening test was conducted using Bradley-Terry-Luce (BTL) model, which was followed by long term avarage spectrum (LTAS) analysis and sound radiation analysis. It was observed that the outcomes were compatible with each other, which suggested that the sound radiation features of the instruments could represent the sound characteristics. At the next step, correlation between the sound radiation of ouds and their vibration features was examined. Measurement of the bridge mobility of the ouds was done and the modal analysis was performed in order to determine the natural frequencies, mode shapes and damping ratios of vibration modes of the instruments. Using the results obtained, the sound radiation features of the instruments were compared, thus the effects of natural vibration modes on sound radiation were determined. At the next stage of the study, effects of the design features of ouds on natural vibration modes were investigated using the finite element method (FEM). As a prior step, it was investigated whether if this method is convenient for examination of the natural vibration modes. For this purpose, 3D finite element model of the empirically produced oud was prepared during the study and theoretical modal analysis was done under structural fluid coupled conditions. The use of the finite element model was justified by comparing the results obtained and the outcomes of the empirical modal analysis. Further, the effects of the design properties on the vibration modes were investigated by modifying the design features of the oud in the finite element model. At the final stage of the study, a research method was suggested for examination of the effects of design features of stringed instruments on sound characteristics. This method was applied to tanbur and baglama as well, and, suggestions were proposed for the general usage of this method for all stringed instruments. In conclusion, information on the sound production processes in the oud and the other stringed instruments included in the study was obtained, and, base on this information, a research method was proposed for determining the design of stringed instruments from the aspect of their sound characteristics. Our results suggest that the proposed method can be used for all stringed instruments.