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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
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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
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Vienna, Boston, Amsterdam
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Orchestra canopies
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Orchestra canopies
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Orchestra canopies
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Panel array canopies
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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
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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
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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
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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
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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
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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
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Support – hearing oneself
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Support – fill-in-effect
w canopy
ST1=-13.7dB
no canopy
ST1=-15.2dB
32ms
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Mutual hearing
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Mutual hearing
♪♫
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Mutual hearing
Fill-in-effect, 10m source-receiver distance
w canopy
no canopy
20dB
20dB
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Mutual hearing
5 measurements, 10m source-receiver distance
w canopy
no canopy
20dB
20dB
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Mutual hearing
Initial time gap, at 10m distance
w canopy
no canopy
20dB
20dB
15ms
48ms
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Height and density – level balance
Low canopies should be transparent
Early-Late balance C80
Stage-Auditorium balance
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Echo-breaker
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Unobstructed sound paths
The canopy path is always available
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Diffuse multi-channel
less dependent on source directivity and obstacles
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Homogenous foldback
t
L
Image orchestra
Received: •In sync •Equal levels
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Option: Inclined surface
t
L Image orchestra
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Wall + Balcony soffit
t
L
Image orchestra
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Transparent canopy - the canopy array
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Flat panel array filter
Transmission
freq F0
Reflection
freq F0
m=60%
s=40%
F0 ~128/a , radius a
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Narrow-band filter canopy
Transmission
freq F0
Reflection
freq F0
s=40%
m=60%
F0 ~128/a , radius a
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Convex panel array filter
Transmission
freq F0
Reflection
freq F0
s=40%
m=60%
F0 ~128/a , radius a
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Two-way panel array filter
Transmission
freq F0
Reflection
freq F0
s=40%
m=60%
F0 ~128/a , radius a
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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
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www.akutek.info
Thank you
The www center for search, research and open sources in acoustics
More info?