Sonic Scenography - Equalized Structure-borne Sound for Aurally Active Set Design

This paper suggests the use of a plywood panel, which is also a scenographic element in a dance performance, as a flat speaker. The sound emanating from the panel is subjectively different from a traditional loudspeaker, since the sound appears to originate from behind the panel. However, its frequency response is severely coloured by the panel modes, and the panel has a displeasing low pass-filtered sound. We propose a digital equalizing filter to improve the sound quality of the panel. The panel response is measured at various angles using the sinesweep method, and a smoothed average response is formed. A minimum-phase FIR equalizing filter is then designed using an FFT-based technique. Applying this filter to the input signal of the panel alleviates the spectral imbalance. As the measurement and filter design can be conducted online on the scene, the proposed equalized structure-borne sound now becomes an attractive possibility for modern performances.