ORCHESTRA CANOPIES

Stage acoustics

Magne Skålevik Brekke & Strand, Oslo, Norway

www.akutek.info

162nd Meeting of the Acoustical Society of America, 2 November 2011, 3aAA1

What is an orchestra canopy?

Horizontal, sound reflecting device

Suspended above orchestra

Element array, m=50% density Single element

These two have equal total surface area

Vienna, Boston, Amsterdam

Orchestra canopies

Orchestra canopies

Orchestra canopies

Panel array canopies

Orchestra, acoustic needs

Hearing others, notes, pitch, ques, intonation Direct sound path obstructed , alternative sound paths

beneficial Transmission quality measure demanded

Early low frequency response, Gearly, 63-125Hz Bass pulse, Beat, to play in sync Heavy walls close to orchestra

Hearing the hall acoustics, performers reverberance Proper STlate , Glate and C on stage Stage not separated from auditorium, no low stage ceiling

No echoes no specular ceiling reflection

Attenuation through orchestra

Higher: Free sightline STI=0.67

Lower: Through orchestra STI=0.55 13dB

No canopy

Transmission IR from 1st Violin to Basson, distance 11m

Chairs+stands w/wo musicians

Higher: Chairs and stands STI=0.65

Lower: Chairs , stands and musicians STI=0.55 10dB

Transmission IR from 1st Violin to Basson, distance 11m

No canopy

Canopy effect, no sightline

Upper: With canopy STI=0.61

Lower: Without canopy STI=0.55

10dB

Transmission IR from 1st Violin to Basson, distance 11m

Two different models, STI

P1P1

0 3 5 8 10 13 15 18 metres

0

3

5

8

10 metres

0,65

0,63

0,61

0,58

0,56

0,53

0,51

0,49

0,46

0,44

0,41

0,39

0,37

0,34

0,32

STI >= 0,70

<= 0,30Odeon©1985-2009 Licensed to: Brekke & Strand Akustikk AS, Norway

P1P1

0 3 5 8 10 13 15 18 metres

0

3

5

8

10 metres

0,66

0,63

0,60

0,57

0,55

0,52

0,49

0,46

0,43

0,41

0,38

0,35

0,32

STI >= 0,70

<= 0,30Odeon©1985-2009 Licensed to: License information /dongle unavailable at start up!Odeon©1985-2009 Licensed to: License information /dongle unavailable at start up!

Odeon©1985-2009 Licensed to: Brekke & Strand Akustikk AS, Norway

STImedian =0.6

STImedian =0.5

Transmission through orchestra, re free sight

Transmission from 1st Violin to Basson, distance = 11m

Freq (Hz)

500

0 dB

-10 dB

1k

Canopy reflection frequency range

2k

Support – hearing oneself

Support – fill-in-effect

w canopy

ST1=-13.7dB

no canopy

ST1=-15.2dB

32ms

Mutual hearing

Mutual hearing

♪♫

Mutual hearing

Fill-in-effect, 10m source-receiver distance

w canopy

no canopy

20dB

20dB

Mutual hearing

5 measurements, 10m source-receiver distance

w canopy

no canopy

20dB

20dB

Mutual hearing

Initial time gap, at 10m distance

w canopy

no canopy

20dB

20dB

15ms

48ms

Height and density – level balance

Low canopies should be transparent

Early-Late balance C80

Stage-Auditorium balance

Echo-breaker

Unobstructed sound paths

The canopy path is always available

Diffuse multi-channel

less dependent on source directivity and obstacles

Homogenous foldback

t

L

Image orchestra

Received: •In sync •Equal levels

Option: Inclined surface

t

L Image orchestra

Wall + Balcony soffit

t

L

Image orchestra

Transparent canopy - the canopy array

Flat panel array filter

Transmission

freq F0

Reflection

freq F0

m=60%

s=40%

F0 ~128/a , radius a

Narrow-band filter canopy

Transmission

freq F0

Reflection

freq F0

s=40%

m=60%

F0 ~128/a , radius a

Convex panel array filter

Transmission

freq F0

Reflection

freq F0

s=40%

m=60%

F0 ~128/a , radius a

Two-way panel array filter

Transmission

freq F0

Reflection

freq F0

s=40%

m=60%

F0 ~128/a , radius a

What I was trying to say

Start by defining what the orchestra needs

Design canopy as a response to needs

Predict difference w/wo canopy Subtle fill-in effect, hard to predict, hard to measure

Don’t use it if you don’t need it Remember Vienna, Amsterdam, Boston

Check for unwanted side-effects Uneven coverage, bad pitch-response, echoes, balance,..

Canopy Arrays useful, but involve many design parameters Element size, frequency range, Density, Height, Diffusivity and Coverage

Effective echo-breaker

Stage Acoustics research far from complete, demand for metric remains Current parameters (ST) apply to empty stage, maybe solo, duet, quartet.......but

not to orchestra conditions Obstructed cross-stage paths must be taken into account

www.akutek.info

Thank you

The www center for search, research and open sources in acoustics

More info?

magne.skalevik@brekkestrand.no