Archontis Politis, Tapani Pihlajamäki, and Ville Pulkki

Parametric Spatial Audio Effects

Companion page for a paper in the 15th International Conference on Digital Audio Effect (DAFx-12), York, UK, September 17–21, 2012

Abstract

Parametric spatial audio coding methods aim to represent efficiently spatial information of recordings with psychoacoustically relevant parameters. In this study, it is presented how these parameters can be manipulated in various ways to achieve a series of spatial audio effects that modify the spatial distribution of a captured or synthesised sound scene, or alter the relation of its diffuse and directional content. Furthermore, it is discussed how the same representation can be used for spatial synthesis of complex sound sources and scenes. Finally, it is argued that the parametric description provides an efficient and natural way for designing spatial effects.

Paper

Demos

All files are rendered for a 5.1 setup using the DirAC method as described in the paper. The binaural versions are generated from a symmetric 8 loudspeaker virtual rendering, converted to binaural using HRTFs from the Listen set by IRCAM.

1. Modification of directional properties

Zooming (via B-format projection)

• 5.1 wave | Binaural | Synthesised recording of an anechoic orchestra distributed between -60° and 60°. After 3 seconds, the scene is gradually zoomed in the frontal direction so that after 15 seconds, the orchestra is distributed between -110° and 110°. Frontal sources are also amplified and the ones on the sides are naturally attenuated.

Spatial filtering

• Reference (5.1) | Reference (Binaural) | 0° (5.1) | 0° (Binaural) | -90° (5.1) | -90° (Binaural) | 90° (5.1) | 90° (Binaural)
  Synthesised recording of an anechoic orchestra distributed between -90° and 90°. The processed recordings correspond to a third order cardioid oriented towards front, left and right respectively. The diffuse sound is generated from a first order cardioid oriented on the same direction.
• Reference (5.1) | Reference (Binaural) | 0° (5.1) | 0° (Binaural) | -90° (5.1) | -90° (Binaural) | 90° (5.1) | 90° (Binaural)
  B-format recording of a string quartet. The processed recordings correspond to a third order cardioid oriented towards front, left and right respectively. The diffuse sound is generated from a first order cardioid oriented on the same direction.

Spatial modulation and morphing

• Modulator (5.1) | Modulator (Binaural) | Mono carrier | Result (5.1) | Result (Binaural)
  Monaural recording of a choir singing sustained notes, modulated with a B-format recording of a percussion performance (from EBU 5.1 reference set converted to B-format)

2. Reverberation and ambience modification

Diffuse field control

• Reference (5.1) | Reference (binaural) | +12 dB (5.1) | +12 dB (binaural) | -12 dB (5.1) | -12 dB (binaural)
  B-format recording of a classical orchestra at the conductor's position, with direct-to-reverberant ratio modified by +12 and -12 dB respectively
• Reference (5.1) | Reference (binaural) | +12 dB (5.1) | +12 dB (binaural) | -12 dB (5.1) | -12 dB (binaural)
  B-format recording of a string quartet (originally recorded by John Leonard and provided to Ambisonia.com), with direct-to-reverberant ratio modified by +12 and -12 dB respectively
• Reference (5.1) | Reference (binaural) | +12 dB (5.1) | +12 dB (binaural) | -12 dB (5.1) | -12 dB (binaural)
  B-format recording of a band playing in a reverberant room, with direct-to-reverberant ratio modified by +12 and -12 dB respectively

Ambience extraction

• Reference | Mono ambience | Extracted ambience from a B-format recording of a band playing in a reverberant room
• Reference | Mono ambience | Extracted ambience from a B-format recording of a string quartet (originally recorded by John Leonard and provided to Ambisonia.com)

3. Spatial sound synthesis

Basic panning

• 5.1 wave | Binaural | Synthetic sound scene of three separate static sources (gun shots, helicopter, radio garble)
• 5.1 wave | Binaural | Synthetic sound scene of three separate static sources (music, speech, grandfather clock)
• 5.1 wave | Binaural | Synthetic sound scene of three separate moving sources (gun shots, helicopter, radio garble)
• 5.1 wave | Binaural | Synthetic sound scene of three separate moving sources (music, speech, grandfather clock)

Spatial extent synthesis

• 5.1 wave | Binaural | Wide marching company moving from right to left in front of the listener
• 5.1 wave | Binaural | Wide marching company moving from front to back surrounding the listener
• 5.1 wave | Binaural | Ambient recording of crickets and birds with widening sound from point source in front to completely surrounding
• 5.1 wave | Binaural | Shotgun firing sound with reverberation included. Spatial extent is rapidly increased after the initial blast to randomly distribute the existing reverberation. (original sample courtesy of Remedy Entertainment Ltd.)