sound reproduction and acoustic enhancement in concert ......31.10.2008 © 2008, sonic emotionag...

31.10.2008 © 2008, sonic emotion ag Slide 1

Sound Reproduction andAcoustic Enhancement in Concert Halls

Using Wave Field Synthesis

Clemens Kuhn-Rahloffsonic emotion ag

[email protected]


Overview

• Sound Field Reproduction – why?

• Principles of Wave Field Synthesis

• Application Example and System Overview

• Active Room Acoustics and Wave Field Synthesis

• Summary

• Questions & Discussions


Overview





• Summary



A short historic overview on spatial sound design

• Spatial sound from early music to contemporary electro-acoustic compositions (sound reproduction).– e.g. Varèse/Xenakis:

Poème électronique (Brüssel, 1958) und Virtual Electronic Poem (Berlin, 2004)

• Aesthetics of spatial sound reinforcement systems – e.g. Pink Floyd (quadrophonic systems in concerts)– Less obstrusive systems especially for classical music (e.g. delta stereophony in the

1980s)

• Aesthetics of room acoustics– Decoupling the physical and aesthetic properties of halls by electro-acoustic room

enhancement systems


Acoustical Design of Rooms• Re-design and re-shape the acoustic properties of the room

regardless of its real physical properties.

• The audio system shall:

– Appear as being a “natural” part of the hall (“inaudible” loudspeaker)– Keep localisation of sound sources and perception of room acoustics

coherent with visual aspects– Create a sonic image independent of the listening position– Open an acoustic space behind the physical walls– Possibly enable virtual rooms that go beyond the scope of plausibility to

achieve new experiences of artistic environments.


Quality measures of spatial soundreproduction

• Meet the requirements of human perception

– Localisation performance– Distance– Room size– Room interaction– …

ÿ Perceptual properties of Wave Field Synthesis as tools for spatial reproduction


Overview





• Summary



Wave Field Synthesis

• Wave Field Synthesis (WFS) Concept:

– Sound source emits certainwave fields

– Reproduction usingsecondary sourcesaccording to HuygensPrinciple



• Arbitrarily shapedsecondary source arrays– Reproduction as point

source: holographicimaging...



• Arbitrarily shapedsecondary source arrays– ...even in front of the

loudspeaker array



– ...or as plane waves (identical image for all listeners at any position inside the loudspeaker array)


Multichannel equalization, sound field control

• Measure of loudspeaker radiation on an ensemble of microphone positions

• Specification of a target sound field (associated to a virtual source position/directivity)

• Multichannel inversion, iterative calculation of filters in the time domain

h2

hi

hn

h1


Multichannel equalization, plane wave

Better frequency response than with conventional equalization

Classical equalization Multichannel equalization


Overview





• Summary



„Neue Aula“, Conservatory of Music Detmold

• Concert Hall with approx. 500 seats• Dimensions:

– Length: 30m + 6 m stage– Width: 18m– Height: 10.5m (stage) / 7.5m (back wall)

• No balcony• Natural reverberation time: 1.6sec• Organ


„Neue Aula“, Conservatory of Music Detmold


Applications

• Concerts of classical music starting from early music to romantic symphonic music and contemporary works.

• Composition and performance of contemporary electro-acoustic pieces

• Optional sound reinforcement for jazz concerts, etc.


System Overview

• 272 loudspeakers WFS

• Ceiling: 41 loudspeakers + 12 subwoofers

• Stage: focused sources• Listening area: point sources „outside“ of the hall• Ceiling: elevated sources


System Overview

Sound Reproduction-

Augmented Reality

panels p075&p150

wave I-III wave control

wave rooms

wave net


panels for wave systems

• panels p075&p150: Flat panel loudspeaker technology. • panels may be integrated in walls, screens or cabinets.


Distributed System Architecture

• wave I-III and engine304– ADAT-input 48kHz, 16bits, 24

inputs, 16 outputs per engine• amp103

– fan-less amplifiers close to the respective loudspeakers

– 25W amplifier output per channel

– Additional amplifiers(100W/200W) for ceiling loudspeakers and subwoofers


Digital Audio Workstations Including wave control


wave system architecture

wave net(parameter communication, TCP/IP)

amplifieramp103

amplifieramp103

amplifieramp103

amplifieramp103

amplifieramp103

System control from -Standard GUI (running on PC or MAC)-Individual software (integration and APIs on request)-...

wave engine with 24 outputs for loudspeaker signals

amplifieramp103

amplifieramp103

amplifieramp103

loudspeaker outputs to panels or other

loudspeakers for WFS25W at 8 Ohms



ADAT

Audio Input for 24 virtual source signals

(ADAT format, 48kHz, 16bits)


Overview





• Summary



Active Room Acoustics

• Room enhancement from 1.6sec up to more than 3sec for a broad repertoire.

• In-line technology:– 6 microphones in the stage area and at the organ– Signal processing in SIAP MkIV processor and wave III– Reproduction of reverberant field using WFS system.


Advantages of Active Room Acoustics with WFS

• Very homogeneous sound field reproduction– Single loudspeaker not perceivable– Higher diffuse sound field level possible compared to

conventional room enhancement systems

• Control of lateral energy (envelopment) due to directivity control of early reflections.

• Virtual enlargement of the room (virtual distance of the walls).


Reverberation Level• Criteria

– You should never be able to indicate the artificial reverberation, thus:

• Enhanced SPL < Natural SPL

– The artificial reverberation should sound natural:• Stability• No Colouration


Reverberation Times

-30,0

-25,0

-20,0

-15,0

-10,0

-5,0

0,0

0,5 0,7 0,9 1,1 1,3 1,5 1,7 1,9 2,1 2,3 2,5 2,7 2,9

Reverberation Time [s]

Reve

rb L

evel

[dB

]

RT = V/6A

p2=4ρcW/A


Reverberation Times• 1.6sec natural reverberation time

• 1.8sec small symphony orchestra

• 2.0sec symphony orchestra

• 2.2sec late romantic symphonic music

• 2.4sec orchestra with choir

• 2.8sec small choir

• 3.2sec large choir

• 6.0sec cathedral experimental setting


Overview





• Summary



Summary

• Tools for designing spatial sound in concert halls

• Enlarging the listening room

• Approaching known workflows and production methods

• Room enhancement using active room acoustics combined with wave field synthesis

ÿ Re-design and re-shape the acoustic properties of the room (almost) regardless of its physical properties.


Thank you for your attention!Thank you for your attention!

www.www.sonicemotionsonicemotion.com.com

© 2008, sonic emotion ag

sound reproduction and acoustic enhancement in concert ......31.10.2008 © 2008, sonic emotionag...

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