Directional Feedback Delay Network
Benoit Alary, Archontis Politis, Sebastian J. Schlecht, Vesa Välimäki · Journal of the Audio Engineering Society · 2019
Artificial reverberation algorithms are used to enhance dry audio signals.Delay-based reverberators can produce a realistic effect at a reasonable computational cost.While the recent popularity of spatial audio algorithms is mainly related to the reproduction of the perceived direction of sound sources, there is also a need to spatialize the reverberant sound field.Usually multichannel reverberation algorithms output a series of decorrelated signals yielding an isotropic energy decay.This means that the reverberation time is uniform in all directions.However, the acoustics of physical spaces can exhibit more complex direction-dependent characteristics.This paper proposes a new method to control the directional distribution of energy over time, within a delay-based reverberator, capable of producing a directional impulse response with anisotropic energy decay.We present a method using multichannel delay lines in conjunction with a direction-dependent transform in the spherical harmonic domain to control the direction-dependent decay of the late reverberation.The new reverberator extends the feedback delay network, retaining its time-frequency domain characteristics.The proposed directional feedback delay network reverberator can produce non-uniform direction-dependent decay time, suitable for anisotropic decay reproduction on a loudspeaker array or in binaural playback through the use of ambisonics.