A Virtual Endfire Loudspeaker Array for the Generation of Sound Beams Sascha Spors 1 and Hagen Wierstorf 2 1Universität Rostock, Institute of Communications Engineering 2Technische Universität Berlin, Assessment of IP-based Applications
Virtual Endfire Loudspeaker Array Drawbacks of superdirective beamforming with endfire loudspeaker arrays • directivity for high frequencies requires small loudspeaker spacing • limited robustness against loudspeaker mismatch • very limited steering of beam possible Virtual endfire array x y 1 2 N . . . • similar to beam generation in parametric arrays • flexible placement of virtual sources • steering of beam by tilting of virtual endfire array Spors, Wierstorf | Virtual Endfire Array | Endfire Loudspeaker Array 5
Focused Sources in Wave Field Synthesis x (m) y (m) −2 −1 0 1 2 0 1 2 3 Amplitude (dB) −40 −30 −20 −10 0 (2.5D WFS, ∆x = 10 cm, L = 4 m) • virtual acoustic sink at focus point • main propagation direction can be chosen by loudspeaker selection [Spors et al. 2007] Spors, Wierstorf | Virtual Endfire Array | Focused Sources 6
Focused Sources in Wave Field Synthesis x (m) y (m) −2 −1 0 1 2 0 1 2 3 Amplitude (dB) −40 −30 −20 −10 0 (2.5D WFS, ∆x = 10 cm, L = 4 m) • virtual acoustic sink at focus point • main propagation direction can be chosen by loudspeaker selection [Spors et al. 2007] Spors, Wierstorf | Virtual Endfire Array | Focused Sources 6
Focused Sources in Wave Field Synthesis x (m) y (m) −2 −1 0 1 2 0 1 2 3 Amplitude (dB) −40 −30 −20 −10 0 (2.5D WFS, ∆x = 10 cm, L = 4 m) • virtual acoustic sink at focus point • main propagation direction can be chosen by loudspeaker selection [Spors et al. 2007] Spors, Wierstorf | Virtual Endfire Array | Focused Sources 6
Conclusions Generation of acoustic beams by two stage approach 1. synthesis of focused sources 2. superdirective beamforming using virtual endfire array • combination of delay-and-sum focusing with superdirective beamforming • achieved gain comparable to other techniques • not limited to linear arrays • reproducible research → Sound Field Synthesis (SFS) Toolbox Outlook • investigation of robustness (loudspeaker mismatch) • incorporate properties of focused sources into beamformer design Spors, Wierstorf | Virtual Endfire Array | Results 13