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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
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
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Thank you
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