Coloration in Wave Field Synthesis Hagen Wierstorf 1 , Christoph - PowerPoint PPT Presentation

Coloration in Wave Field Synthesis Hagen Wierstorf 1 , Christoph Hohnerlein 1 , Sascha Spors 2 , Alexander Raake 1 1 Assessment of IP-based Applications, TU Berlin 2 Institut für Nachrichtentechnik, Universität Rostock 29. August 2014

Introduction Focus of evaluation of spatial audio systems is on spatial aspects key aspect we are working on relatively easy to investigate and to model What other aspects do we have to consider? Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 1 / 13

Introduction If it sounds bad, the spatial aspects don’t matter artefacts can become audible for focused sources in WFS (Wierstorf 2013) perceived quality is determined by 70% by timbral aspects in 5.1 stereophony (Rumsey 2005) coloration in WFS? Rumsey et al. (2005), On the relative importance of spatial and timbral fidelities in judgments of degraded multichannel audio quality, JASA Wierstorf et al. (2013), Perception of Focused Sources in Wave Field Synthesis, JAES Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 2 / 13

Timbre Timbre is most often defined as that attribute of auditory sensation which enables a listener to judge that two nonidentical sounds, similarly presented and having the same loudness and pitch, are dissimilar (ANSI 1994) similarly presented? ⇒ other authors used more explicit definition: The label timbre combines all auditory object attributes other than pitch, loudness, duration, spatial location and reverberation environment. (Emiroglu, 2007) timbral space is multidimensional and underlying metric non-trivial ANSI (1994), American National Standard Acoustical Terminology, ANSI S1.1-1994 Emiroglu (2007), Timbre perception and object separation with normal and impaired hearing, PhD-thesis, Oldenburg Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 3 / 13

Timbre Timbre is most often defined as that attribute of auditory sensation which enables a listener to judge that two nonidentical sounds, similarly presented and having the same loudness and pitch, are dissimilar (ANSI 1994) similarly presented? ⇒ other authors used more explicit definition: The label timbre combines all auditory object attributes other than pitch, loudness, duration, spatial location and reverberation environment. (Emiroglu, 2007) timbral space is multidimensional and underlying metric non-trivial ANSI (1994), American National Standard Acoustical Terminology, ANSI S1.1-1994 Emiroglu (2007), Timbre perception and object separation with normal and impaired hearing, PhD-thesis, Oldenburg Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 3 / 13

Coloration Coloration can then be defined as the difference of two points in the timbral space, whereby one of the points is the reference and the other point is colored. (Brüggen 2001) has the reference point always a better quality? influence of concert halls is a desired coloration Brüggen (2001), Klangverfärbungen durch Rückwürfe und ihre auditive und instrumentelle Kompensation, PhD-thesis, Bochum Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 4 / 13

Coloration and WFS Why do we have coloration in Wave Field Synthesis? WFS is implemented by delaying and weighting the same audio signal ⇒ highly correlated loudspeaker signals ⇒ comb-filter like spectrum Research question: dependency on the number of used loudspeaker change with the listening position Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 5 / 13

Inter-System Coloration Experimental Setup virtual microphone at ( − 0 . 1 , 0 , 0) m 360 320 0 . 3 cm 280 0 . 5 cm sound pressure / dB 240 1 cm 200 2 cm 160 4 cm 120 WFS 8 cm 80 17 cm 40 34 cm 0 67 cm − 40 stereo − 80 − 120 100 400 1 k 4 k 10 k frequency / Hz Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 6 / 13

Inter-System Coloration Experimental Setup 15 listeners pulsed pink noise + speech HRTF for head orientation φ MUSHRA point source as reference 5 kHz high-pass as low head tracker SSR dry convolution and anchor head orientation φ audio material HRTF switching 9 different WFS systems stereophony static binaural simulation using non-individual HRTFs simulated loudspeakers Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 7 / 13

Inter-System Coloration Experimental Setup 15 listeners pulsed pink noise + speech HRTF for head orientation φ MUSHRA point source as reference 5 kHz high-pass as low head tracker SSR dry convolution and anchor head orientation φ audio material HRTF switching 9 different WFS systems stereophony static binaural simulation using non-individual HRTFs simulated loudspeakers Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 7 / 13

Inter-System Coloration Results very listener at (0 , 0 , 0) m different perceived coloration noise speech no WFS difference ref stereo 0 . 3 cm 0 . 5 cm 1 cm 2 cm 4 cm 8 cm 17 cm 34 cm 67 cm low system Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 8 / 13

Intra-System Coloration What happens if we move the source/listener within a system? extremely different intra-system coloration noise perceived no WFS difference real stereo 3 cm 12 cm 24 cm 48 cm system Wittek (2007), Perceptual differences between Wave Field Synthesis and stereophony, PhD-thesis, Surrey Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 9 / 13

Intra-System Coloration Experimental Setup loudspeaker spacing 17 cm 440 400 360 sound pressure / dB 320 280 240 200 WFS 160 120 80 40 0 − 40 100 400 1 k 4 k 10 k frequency / Hz Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 10 / 13

Intra-System Coloration Results perceived coloration 10 very different 5 0 no difference 0 . 17 m noise speech 5 4 4 4 5 0 4 3 3 3 3 0 4 4 5 4 8 4 3 3 3 5 WFS Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 11 / 13

Conclusions typical WFS systems show high amount of coloration both inter- and intra-system depends directly on the aliasing frequency temporal aspects of coloration crucial for focused sources in WFS (Wierstorf 2013) Wierstorf et al. (2013), Perception of Focused Sources in Wave Field Synthesis, JAES Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 12 / 13

Questions? http://twoears.eu http://spatialaudio.net http://gnuplotting.org Wierstorf, Hohnerlein, Spors, Raake 29.08.14 Coloration in Wave Field Synthesis 13 / 13