Music Performance with Variable Reflection Acoustic Wall System

Department� ofAcousticDesignFaculty� of� DesignKyushu� University

Forum Acusticum 2014

Music Performance with Variable Reflection Acoustic Wall System

Akira Omoto Faculty of Design / Kyushu University

Takahiro Nishiyama, Yuki Yoshimura Graduate School of Design / Kyushu University



Table of Contents

n Introduction

n Variable Reflection Acoustic Wall System: VRAWS n Concept n Application

n G-VRAWS n Concept n Basic Performance

n Experimental Concert n Venue and Contents n System Arrangement n On-site state and Impressions from Audience

n Concluding Remarks

2



Introduction

n Motivations n Enhancement of Online Digital Source / Other Digital Stuff

✤ Simultaneous supply of performance to another place, such as movie theater ✤ Extend the chance to experience many contents at distant places ✤ What can an acoustician do?

✓ Sound Reinforcement, Mixing, Public Address, …

✓ Sound Field Reproduction or Creation by Acoustical Technology

➡ Introduction of Variable Reflection Acoustic Wall System

n Cultural Hall Management Engineer Training Program at Kyushu University

✤ Training knowledge, skills, abilities of ✓ stage, lighting, and acoustical engineering required theaters, concert halls

✓ sensibility for art and culture

✓ public policy for promoting artistic and cultural activities

✓ planning and operation of artistic and cultural activities

3



Introduction

n Motivations (contd.) n Cultural Hall Management Engineer Training Program at Kyushu University

✤ Extend the chance for efficient use of cultural hall by acoustical technology ✓ Performance with new technology → extend the expression of arts ✓ Seminar: concept planning, negotiation with artist, selling ticket, publicity, on-site

management ✤ Experimental Concert

✓ Music lesson for distant student (elementary school, junior high school) ✓ Distant session ✓ Several types of music with different reverberation in small hall

4



Variable Reflection Acoustic Wall System

n Concept n Microphone + Absorbing Material + Loudspeaker = Arbitral Reflection

✤ Signal flow

5





✤ Signal flow

5

Incident Sound





✤ Signal flow

5

Incident Sound

Pick up incident sound





✤ Signal flow

5

Incident Sound


Additional effector Reverb, etc…





✤ Signal flow

5

Incident Sound



Re-radiated Sound

Absorbing material with high transmission ratio





✤ Signal flow

5

Incident Sound



Re-radiated Sound

Adaptive Howling CancelerAbsorbing material with

high transmission ratio




n Concept n Microphone + Absorbing Material + Loudspeaker

✤ Features

6

‣ Re-radiate incident sound from behind the absorbing material

‣ On the basis of high transmission ratio of absorbing material

‣ Arbitrary modification could be introduced for re-radiating sound

‣ Effective howling canceler would be needed

Variable Ampritude

Re-radiated Reflection

Incident Sound

Microphone to Pick-Up

Incident Sound

Arbitrary Effector

Absorbing Material with

High Transmission Ratio

Reflection from Surface

Feedback Canceller

-�

Reverb

Effe

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r e

tc

Sim

ula

ted

Im

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lse

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se

betw

ee

n M

icro

ph

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nd

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ea

ke

r

Loudspeaker(s) Mounted

behind Material




n Application n Change the characteristics in small sized enclosure, studio, music practice room

7




n Application n Variations

8

A speaker installationon the bottom

QRD installation on all sides inside

Styrene balls of various sizes installation

Absorbing material in chinks and surface Originally designed two-way version




n Application n Variations: mainly for increasing howling margin by strong directivity

9

Flat dynamic loudspeaker version Distributed Mode Loudspeaker (DML) version




n Application n Variations: mainly for increasing howling margin by strong directivity

9

Flat dynamic loudspeaker version Distributed Mode Loudspeaker (DML) version

Mic. at Node




n Application n Preliminary experiment with Originally designed two-way VRAWS

10




n Application n Preliminary experiment with Originally designed two-way VRAWS

10

Distant session with dedicated line Atmosphere of distant venue was varied by VRAWS




n Application n Two functions of VRAWS: Sound Reinforcement + Additional Reverb

11

Ȉ

Ȉ

Ȉ

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Rev-2

Rev-1

Rev-1

TransmittedSignal

System-IDReverb+

-

+

+

++

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VRAWS

Main Speaker

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Amp.

DPA 4099 YAMAHA HA-8

YAMAHASPX2000

AMCROND-45

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(1)

(2)(3)

(4)

(5)

(6)

(7)(8)

(9)

Howling Canceler





11

Ȉ

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Rev-2

Rev-1

Rev-1

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System-IDReverb+

-

+

+

++

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VRAWS

Main Speaker

0L[HU

([WHUQDO(IIHFWRU

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YAMAHASPX2000

AMCROND-45



(1)

(2)(3)

(4)

(5)

(6)

(7)(8)

(9)

Howling Canceler

Sound Reinforcement with appropriate effector





11

Ȉ

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Rev-1

Rev-1

TransmittedSignal

System-IDReverb+

-

+

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Main Speaker

0L[HU

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YAMAHASPX2000

AMCROND-45



(1)

(2)(3)

(4)

(5)

(6)

(7)(8)

(9)

Howling Canceler

Sound Reinforcement with appropriate effector

Adding Reverb at Reproducing Sound Field - VRAWS -



G-VRAWS

n Concept n Hi-Fi VRAWS with Genelec: Multi Purpose Reproduction System

12

Absorbing Material

Genelec 8020C



G-VRAWS


12

Absorbing Material

Genelec 8020C

3 x 12 = 36ch Multi Purpose Sound Field Reproduction System



G-VRAWS


12

Absorbing Material

Genelec 8020C

3 x 12 = 36ch Multi Purpose Sound Field Reproduction System

JSPS KAKENHI Grant Number 25282003



G-VRAWS

n Basic Performance n Frequency Characteristics

13

100 1000 1000040

50

60

70

80

90

Without Absorber

With Absorber

Frequency [Hz]

Re

lative L

eve

l [d

B]



G-VRAWS

n Basic Performance n Directivity with and without Absorbing Material

14

125 Hz

250 Hz

500 Hz

1 kHz

2 kHz

4 kHz

With

Ab

so

rbe

rW

ith

ou

t A

bso

rbe

r

50 dB 50 dB 50 dB



G-VRAWS

n Basic Performance n Amplitude of Re-generated Reflections

15

2.55 m 3.16 m

Measurement Microphone

Primary Loudspeaker emittingSwept Sine Signal

Microphone to Pick UpIncident Sound

Absorbing Material

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Time [ms]

Re

lative

Le

ve

l [d

B]

Re

lative

Le

ve

l [d

B]

Re

lative

Le

ve

l [d

B]

G-VRAWS: Off

G-VRAWS: On

G-VRAWS: On

Reverb: Off

Reverb: On



Re-radiated Reflection

Added Reverberation

Direct Sound



G-VRAWS

n Basic Performance n Reverberation Curves

16

2.55 m 3.16 m

Measurement Microphone

Primary Loudspeaker emittingSwept Sine Signal

Microphone to Pick UpIncident Sound

Absorbing Material

0 200 400 600 800 1000

í��

í��

í��

í��

í��

í��

í��

0

G-VRAWS: Off

G-VRAWS: On

G-VRAWS: On

Reverb: Off

Reverb: On

Time [ms]

Re

lative

Le

ve

l [d

B]



G-VRAWS

n Basic Performance n Equivalent Absorption Area / One G-VRAWS

17

Frequency [Hz] 250 500 1000 2000 4000

A [m 0.76 1.25 1.77 1.80 1.76

Measured in reverberation chamber with three G-VRAWS. The results were then divided by three.



Experimental Concert

n Venue and Contents n Venue

✤ Small sized multi-purpose hall in Kyushu University (TAJIGEN-Hall) ✤ Octagonal Shape, Flat Floor, Capacity: approx. 300 ✤ Potentially Dead Space : Reverberation Time 1.3 s !!!

n Contents

✤ Classical music with flute and gut guitar

✤ Jazz session of sax and piano including distant session

✤ Media-art performance with computer generated sound and guitar

18

Frequency [Hz] 250 500 1000 2000 4000

RT [s] 1.31 1.35 1.32 1.31 1.14




n System Arrangement n Block diagram

19

D/A

A/D

front frontmidmid

rear rearrearrear

G-VRAWS

Mixer forSR

Optical TEL Optical TEL

Dedicated Line in University

Performance Area

Performance Area

Studio : Distant VenueMulti Purpose Hall

1

2

3

4

5

6

7

8

For Function-A of G-VRAWS, detected sound is firstly directed to PC after passing through mixer for sound reinforcement.Impulse responses measured in concert hall are then convoluted and radiated from G-VRAWS. These responses are measured at the vicinity of walls of hall, in the front, middle, and rear positions.

ProToolswith

Waves IR-1

Audience Area

Function-B of G-VRAWS is available for eight systems due to the limitted number of hardware (they are numberd in the figure). Another four systems are connencted in parallel.

For Basic Sound Reinforcement

Main Venue




n On-site state

20

G-VRAWS surrounding audience




n On-site state

20


Classic music: Flute and Guitar

Reverberation Time of G-VRAWS Function B was set to 2.4 s




n On-site state

20




Jazz Session of Sax and Piano including Distant Session





n On-site state

20




Jazz Session of Sax and Piano including Distant Session


Media-art Performance and Session with guitar





n Impressions from Audience n Good

✤ Comfortable reverberation and envelopment ✤ Natural impression of reverb and stereophonic effect ✤ Natural feeling for distant session ✤ Interesting change of reverb to match the music ✤ …

n Bad ✤ Non-natural balance reinforcement system ✤ Too much reverberation ✤ Latency of visual signal compared with sound ✤ …

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Concluding Remarks

n Concert with Variable Reflection Acoustic Wall System n VRAWS

✤ Artificial reverberation by sound radiation from behind the absorbing material ✤ Possibility to extend the characteristics of sound field ✤ Basically suitable for small sized enclosure ✤ Needs more howling margin… ✤ Needs simple system structure…

n Concert ✤ Experimental concert with 12 VRAWS ✤ Recognizable changes for audience ✤ Possibility of usability in large space ✤ More and more channels…

✤ Expanding Characteristics of Sound Field = Possibility of New Contents!

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Thank you very much for your kind attention.

Music Performance with Variable Reflection Acoustic Wall System

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