Treating seat-dip with acoustic metamaterials and detuned acoustic resonators

Abstract

As sound passes over regularly spaced audience seating areas in performance spaces at a grazing angle, the low frequency response of performing arts venues and auditoria is altered. This is due to diffraction based on the regular spacing of the seating. One effect is what is referred to as seat-dip attenuation, which is a reduction in low frequency energy across a bandwidth. Being a low-frequncy phenomenon, it is difficult to treat using conventional acoustic materials such as porous absorbers or Schroeder diffusers. Modern acoustic metamaterials can alter wave propagation using relatively thin layers. This project investigates whether acoutic metamaterials applied to the tops of the seats, the rear of the seats, or the floor can reduce the low-frequency attenuation brought about by the seat-dip effect. This novel approach demonstrates varying levels of succes for remediating low-frequency seat-dip attenuation. The study is carried out using a computer model that is evualted using boundary element method (BEM) in COMSOL Multiphysics. Additionally, a novel approach for reducing the prominence of the seat-dip effect is explored using detuned Helmholtz resonatos placed at the top of the seats.