Seeking for spectral manipulation of the sound of musical instruments using metamaterials

Abstract

The sound of practically all traditional musical instruments is unique and depends on the collective behavior of various vibrators, each one with their own acoustic and mechanical properties. If we pluck a string of an acoustic guitar, a part of the wave is reflected by the sound box, and the other fraction of the elastic energy sets in motion the sound box surfaces. Thereby, the vibration of the surfaces (soundboard, ribs, back and sound hole), are the basis of the guitar sound production. In this work, we explore the effect of locally coupling tunable mechanical metamaterials to the soundboard of an acoustic guitar, in order to absorb specific ranges of frequencies and change its vibrational properties. We show the preliminary results of our research, which involves a mechano-acoustic characterization of tunable mechanical metamaterials and the analysis of the effect of applying them to an acoustic guitar when a string tuned to a convenient frequency is plucked. We observe that this simple mechanism is an alternative to manipulate the spectral properties of the sound signal produced by the instrument. Although the results are inaudible, they seem promising for future explorations of sound manipulation of musical instruments.