Acoustical effect of progressive undercutting of percussive aluminum bars Free

Standard vibraphone bars consist of aluminum beams which are traditionally tuned with an arched undercut, for the purpose of aligning the musical overtones harmonically. The acoustical effect of various progressions of undercuts on aluminum bars was studied experimentally and with a finite element computer model. The spectral signature of the aluminum bar was determined with a spectrum analyzer, and the corresponding eigenmodes were imaged with an electronic speckle pattern interferometer. These methods were used to analyze the changes in natural frequencies of the bar as material was removed from various locations. The finite element model was used to verify a set of qualitative rules governing the frequency changes, and as a guide in the design of bars with custom harmonic overtone ratios.