Analiza korelacije između mehaničkih i akustičkih osobina kontrabasa

Abstract

U ovoj tezi predstavljene su i testirane metode za analizu zvuka i vibracija kontrabasa. Upotrebom numeričkih modela modelovani su rezonatorska kutija kontrabasa upotrebom metode konačnih elemenata, kao i interakcija između gudala i žice upotrebom metode konačnih razlika. Ponašanje ovih složenih vibroakustičkih sistema analizirano je u slučajevima različitih promena geometrije i njegovih mehaničkih karakteristika. Parametri koji su posmatrani su vibracije na telu instrumenta i gudalu ali i zvuk koji instrument zrači u prostor. Merenja vibracija akcelerometrom kao i snimanje modova oscilovanja skeniranjem u veoma bliskom polju vršena su na gudalu kontrabasa kako bi se identifikovali parametri koji mogu biti ocena kvaliteta nekog gudala. Skeniranje u veoma bliskom polju korišćeno je i u svrhe određivanja mehaničkih osobina drveta kao materijala za izradu muzičkih instrumenata. Ovom metodom ispitivan je i uticaj dugotrajnih vibracija na vibroakustičke osobine drveta. Uticaj anizotropnosti drveta kao materijala na zračenje instrumenta kao i na formiranje modova na ploči takođe je analiziran u ovom radu.

The methods for double bass sound and vibration analysis are presented and tested in this thesis. By using numerical models, double bass body is modeled with finite element method, as well as the interaction between the bow and the string, using the finite difference method. The behavior of these complex vibro-acoustical systems was analysed in the cases of various changes in geometry and its mechanical properties. The vibrations on the instrument body and bow are the parameters that were observed but also the sound that the instrument radiates into the space. Vibration measurements with an accelerometer and modes recording with very near field scanning were carried out on a double bass bow in order to identify the parameters that can be used for the quality evaluation of a bow. Very near field scanning is used to determine the mechanical properties of wood as a material for making musical instruments. This method was also used for the measurement of the impact of prolonged vibrations on the vibro-acoustic properties of wood. The influence of the anisotropy of wood on the radiation of the instrument as well as its influence on the mode shapes formed on the sound board was also analysed in this thesis.