technology in architecture lecture 16 acoustics—historical overview acoustical design acoustics...
TRANSCRIPT
Technology in ArchitectureTechnology in ArchitectureTechnology in ArchitectureTechnology in Architecture
Lecture 16Acoustics—Historical Overview
Acoustical DesignAcoustics Fundamentals
Lecture 16Acoustics—Historical Overview
Acoustical DesignAcoustics Fundamentals
Historic OverviewHistoric OverviewHistoric OverviewHistoric Overview
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
Today
Research to improve conditions for Industrial noise Hearing risks Construction noise Public health
Historic OverviewHistoric Overview
Acoustical DesignAcoustical DesignAcoustical DesignAcoustical Design
Architect’s RoleArchitect’s Role
Source Path Receiver
slight major design primarily interestinfluence
Acoustical DesignAcoustical Design
“Proper acoustical planning eliminates many acoustical problems
before they are built”
Lee Irvine
Acoustical Design Acoustical Design RelationshipsRelationships
SiteLocation
OrientationPlanning
Internal Layout
SiteSite
Match site to applicationMatch application to site
SiteSite
Factory: Close to RR/Hwy Seismic
SiteSite
Rest Home: Traffic Noise Outdoor Use Contact/Isolation
SiteSite
Concert Hall: Use building as isolator Distance from noise
LocationLocation
Take advantage of distance/barriers
Distance
LocationLocation
Take advantage of distance/barriers
Natural or Man-made Berm
LocationLocation
Take advantage of distance/barriers
Acoustical Barriers
LocationLocation
Take advantage of distance/barriers
Building
OrientationOrientation
Orient Building for Acoustical Advantage
Playground School
OrientationOrientation
Orient Building for Acoustical Advantage
Parking Lot Factory
Office
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
Basic Acoustic GoalsBasic Acoustic Goals
1. Provide adequate isolation2. Provide appropriate acoustic
environment3. Provide appropriate internal function4. Integrate 1-3 amongst themselves and
into comprehensive architectural design
Acoustics FundamentalsAcoustics FundamentalsAcoustics FundamentalsAcoustics Fundamentals
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
SoundSound
Any unwanted sound
NoiseNoise
Sound travels at different speeds through various media.
Media Speed (C)
Air: 1,130 fpsWater: 4,625 fpsWood: 10,825 fpsSteel: 16,000 fps
Sound PropagationSound Propagation
Distance between similar points on a successive wave
C=fλ or λ=C/f
C=velocity (fps)f=frequency (hz)λ=wavelength (ft)
Lower frequency: longer wavelength
WavelengthWavelength
λ
Sound Power (P)Sound Intensity (I)
Sound MagnitudeSound Magnitude
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