Institute of Systematic Musicology
Abstract :
Acoustic metamaterials are complex geometries leading to acoustic
behavior not found in natural material, like negative stiffness or
refraction, cloaking or spectral bandgaps. Indeed musical instruments
are complex structures and some may already qualify as
metamaterials. Still altering the instrument geometries and adding
metamaterial behavior can increase the instruments sound variability
and articulatory possibilities or lead to sounds not expected from
mechanical instruments at all. The paper presents such examples.
When modifying a frame drum by adding additional point masses
forming a ring, the frame drum shows cloaking behavior when struck
in the middle of the ring, where frequencies within a certain
frequency band cannot leave the ring. This leads to a bandgap in the
spectrum in the mid frequency range. Still when striking the drum
outside the ring a normal drum sound is achieved. Therefore a
drummer can produce sounds not known from drums before while
with the same instrument can also play regular sounds. Other
examples are modified guitar top plates with added point masses or
waveguide structures.