Analysis of natural frequencies of concert harp soundboard shapes

Abstract

Two possible soundboard shapes for a concert harp were modeled and their lowest natural frequencies compared in order to evaluate the claim that a harp with a bulbous extension has richer sound in the lower notes than one with a simple trapezoidal shape. Two models for the soundboards were evaluated, the first using a stiff plate approximation and the second using a membrane approximation. The lowest modes and frequencies generated by the two models agreed fairly well, and the simpler membrane model was used for the remainder of the analysis. The natural frequencies of an actual harp were determined by impulse response and the frequency spectrum was compared with the modeled frequencies for soundboard and strings. It was determined that many of the important frequencies in the region under 250 Hz could be attributed to the strings. Powerful resonances and clusters coincided with features of the model, indicating that it contains useful qualitative information.