Numerical and experimental studies on the effects of stage risers

The acoustic effects of stage risers, especially on the sound of lower string instruments, are numerically and experimentally analyzed. To discuss the effects of the vibration of riser’s boards due to the mechanical force from an instrument, a structural–acoustical coupling approach is applied based on the mode expansion and the boundary element technique. Measurement results of the mechanical force from real instruments are used in the numerical study. The vibration of the top board of a riser affects the sound field only around the natural frequencies of the board and the cavity of the riser. In contrast, the acoustic diffraction due to the riser affects the sound field in a wide frequency range. The riser’s sideboard that faces to receiving points increases the sound pressure levels because it reflects waves diffracted at the riser’s edge to the front. To verify the numerical results, the effects of acoustic diffraction due to risers are especially investigated in detail through a scale model experiment.