technology in architecture
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Technology in Architecture. Lecture 16 Historic Overview Acoustical Design Sound in Enclosed Spaces Reverberation. Historic Overview. Greek Theatre Open air Direct sound path No sound reinforcement Minimal reverberation. S: p. 785, F.18.17a. Historic Overview. 1 st Century AD - PowerPoint PPT PresentationTRANSCRIPT
Technology in ArchitectureTechnology in ArchitectureTechnology in ArchitectureTechnology in Architecture
Lecture 16Historic OverviewAcoustical Design
Sound in Enclosed SpacesReverberation
Lecture 16Historic OverviewAcoustical Design
Sound in Enclosed SpacesReverberation
Historic OverviewHistoric Overview
Greek Theatre Open air Direct sound path No sound reinforcement Minimal reverberation
S: p. 785, F.18.17a
Historic OverviewHistoric Overview
1st Century ADVitruvius: “10 Books of Architecture”
Sound reinforcementReverberation
S: p. 785, F.18.17b
Acoustical Design—Architect’s Acoustical Design—Architect’s RoleRole
Source Path Receiver
slight major design primarily interestinfluence
Acoustical Design Acoustical Design RelationshipsRelationships
SiteLocation
OrientationPlanning
Internal Layout
SiteSite
Factory: Close to RR/Hwy Seismic
SiteSite
Rest Home: Traffic Noise Outdoor Use Contact/Isolation
LocationLocation
Take advantage of distance/barriers
Distance
LocationLocation
Take advantage of distance/barriers
Acoustical Barriers
OrientationOrientation
Orient Building for Acoustical Advantage
Playground School
Note: Sound is 3-dimensional, check overhead for flight paths
PlanningPlanning
Consider Acoustical Sensitivity of Activities
Noisy Quiet
Barrier
PlanningPlanning
Consider Acoustical Sensitivity of Activities
Critical
Non-Critical
Noise
Internal LayoutInternal Layout
Each room has needs that can be met by room layout
I: p.116 F.5-12
Mechanical vibration, physical wave or series of pressure vibrations in an elastic medium
Described in Hertz (cycles per second)
Range of hearing: 20-20,000 hz
Acoustical Fundamentals—Acoustical Fundamentals—SoundSound
Sound PowerSound Power
Energy radiating from a point source in space.
Expressed as watts
S: p. 750, F.17.9
Sound IntensitySound Intensity
Sound power distributed over an area
I=P/A
I: sound (power) intensity, W/cm2
P: acoustic power, wattsA: area (cm2)
Intensity LevelIntensity Level
Level of sound relative to a base reference
S: p. 750, T.17.2
“10 million million: one”
Intensity LevelIntensity Level
Extreme range dictates the use of logarithms
IL=10 log (I/I0)
IL: intensity level (dB)I: intensity (W/cm2)I0: base intensity (10-16 W/cm2, hearing
threshold)Log: logarithm base 10
Intensity Level Scale Intensity Level Scale ChangeChange
Changes are measured in decibels
scale change subjective loudness3 dB barely perceptible6 dB perceptible7 dB clearly perceptible
Note: round off to nearest whole number
Intensity Level—The MathIntensity Level—The MathIf IL1=60 dB and IL2=50dB, what is the total sound intensity?
1. Convert to intensity
IL1=10 log (I1/I0) IL2=10 log (I2/I0)
60=10 log(I1/10-16) 50=10 log(I2/10-
16)6.0= log(I1/10-16) 5.0= log(I2/10-16)
106=I1/10-16 105=I2/10-16
I1=10-10 I2=10-11
Intensity Level—The MathIntensity Level—The MathIf IL1=60 dB and IL2=50dB,
what is the total sound intensity?
2. Add together
I1+I2=1 x 10-10 + 1 x 10-11
ITOT=11 x 10-11 W/cm2
Intensity Level—The MathIntensity Level—The MathIf IL1=60 dB and IL2=50dB,
what is the total sound intensity?
3. Convert back to intensity
ILTOT= 10 Log (ITOT/I0)
ILTOT=10 Log (11 x 10-11 )/10-16
ILTOT=10 (Log 11 + Log 105 )
ILTOT=10 (1.04 +5) = 60.4 dB
Intensity LevelIntensity Level
Add two 60 dB sources
ΔdB=0,
add 3 db to higher
IL=60+3=63 dB
S: p. 753, F.17.11
Sound Pressure LevelSound Pressure Level
Amount of sound in an enclosed space
SPL=10 log (p2/p02)
SPL: sound pressure level (dB)p: pressure (Pa or μbar)p0: reference base pressure (20 μPa
or 2E-4 μbar)
PerceivePerceived Soundd Sound
Dominant frequencies affect sound perception
S: p. 747, F.17.8
Sound Meter—”A” Sound Meter—”A” WeightingWeighting
Sound meters that interpret human hearing use an “A” weighted scale
dB becomes dBA
Sound In Enclosed Spaces—Sound Absorption
Amount of sound energy not reflected
S: p. 771, , F.18.2
Sound AbsorptionAbsorption coefficient
α=Iα/Ii
α=absorption coefficient Iα=sound power intensity absorbed (w/cm2)Ii=sound power impinging on material (w/cm2)
1.0 is total absorption
Sound AbsorptionAbsorption coefficient
S: p. 769, T.18.1
Sound Absorption
Absorption
A=Sα
A=total absorption (sabins)
S=surface area (ft2 or m2)α=absorption coefficient
sabins (m2)= 10.76 sabins (sf)
Sound Absorption
Total Absorption
Σα=S1α1 + S2α2 + S3α3 +…+Snαn
or
ΣA=A1 + A2 + A3 +…+An
Sound Absorption
Average Absorption
αavg=ΣA/S
αavg <0.2 “live”
αavg >0.4 “dead”
S: p. 774, F.18.6
Reflection in enclosed Reflection in enclosed spacesspaces
Acoustical phenomena
S: p. 787, F.18.20
S: p. 788, F.18.21
Ray diagramsRay diagrams
Trace the reflection paths to and from adjoining surfaces
angle of incidence = angle of reflection
I R
Ray diagramsRay diagrams
Trace the reflection paths to receiver
Reflected sound path ≤ Direct sound path+55
Note: check rear wall and vertical paths
Note: SR-6=RR-7 SR-6: p.116, F.5-12
Reflection inReflection inenclosed spacesenclosed spaces
Auditorium sound reinforcement
S: p. 789, F.18.23
ReverberationReverberation
Persistence of sound after source has ceased
S: p. 771, F.18.2
Reverberation TimeReverberation Time
Period of time required for a 60 db drop after sound source stops
TR= K x V/ΣA
TR: reverberation time (seconds)
K: 0.05 (English) (0.049 in SR-6) or 0.16 (metric)
V: volume (ft3 or m3)ΣA: total room absorption, sabins (ft2 or m2)
Reverberation TimeReverberation Time
ApplicationVolume
S: p. 782, F.18.13
ft3x1000 3.5 35.0 350
Reverberation ExampleReverberation Example
Compile data Material Absorption
Coefficient Material Surface Area
SR-6: p.121
Reverberation ExampleReverberation Example
Compare to requirements and adjust
S: p. 782, F.27.13
ft3x1000 3.5 35.0 350