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

Coloration in Wave Field Synthesis

Hagen Wierstorf1, Christoph Hohnerlein1, Sascha Spors2, Alexander Raake1

1Assessment 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?

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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

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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

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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

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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

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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

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Inter-System Coloration

Experimental Setup

−120 −80 −40 40 80 120 160 200 240 280 320 360 100 400 1k 4k 10k sound pressure / dB frequency / Hz

virtual microphone at (−0.1, 0, 0) m WFS 0.3 cm 0.5 cm 1 cm 2 cm 4 cm 8 cm 17 cm 34 cm 67 cm stereo

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Inter-System Coloration

Experimental Setup

15 listeners pulsed pink noise + speech MUSHRA

point source as reference 5 kHz high-pass as low anchor 9 different WFS systems stereophony

static binaural simulation using non-individual HRTFs

HRTF for head orientation φ SSR convolution and

HRTF switching

head tracker

head orientation φ

dry audio material simulated loudspeakers

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Inter-System Coloration

Experimental Setup

15 listeners pulsed pink noise + speech MUSHRA

point source as reference 5 kHz high-pass as low anchor 9 different WFS systems stereophony

static binaural simulation using non-individual HRTFs

HRTF for head orientation φ SSR convolution and

HRTF switching

head tracker

head orientation φ

dry audio material simulated loudspeakers

Wierstorf, Hohnerlein, Spors, Raake Coloration in Wave Field Synthesis 29.08.14 7 / 13

Inter-System Coloration

Results

no difference very different

ref stereo 0.3 cm 0.5 cm 1 cm 2 cm 4 cm 8 cm 17 cm 34 cm 67 cm low perceived coloration system

WFS noise speech listener at (0, 0, 0) m

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Intra-System Coloration

What happens if we move the source/listener within a system?

no difference extremely different

real stereo 3 cm 12 cm 24 cm 48 cm perceived intra-system coloration system WFS

noise

Wittek (2007), Perceptual differences between Wave Field Synthesis and stereophony, PhD-thesis, Surrey

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Intra-System Coloration

Experimental Setup

−40 40 80 120 160 200 240 280 320 360 400 440 100 400 1k 4k 10k sound pressure / dB frequency / Hz

loudspeaker spacing 17 cm WFS

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Intra-System Coloration

Results

5 4 4 4 5 8 4 5 4 4

noise

3 3 3 3 4 5 3 3 3 4

speech perceived coloration very different no difference 5 10 WFS

0.17 m Wierstorf, Hohnerlein, Spors, Raake Coloration in Wave Field Synthesis 29.08.14 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

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Questions?

http://twoears.eu http://spatialaudio.net http://gnuplotting.org

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