1. Environmental Controls I/IG
Lecture 20
Acoustics—Historical Overview
Acoustical Design
Acoustics Fundamentals

2. Historic Overview

3. Historic Overview Greek Theatre Open air Direct sound path
No sound reinforcement
Minimal reverberation
S: p. 775, F.18.17a

4. Historic Overview 1st Century AD Vitruvius: “10 Books of Architecture”
Sound reinforcement
Reverberation
S: p. 775, F.18.17b

5. Historic Overview Late 1700s-early 1800s
Acoustics developed as part of physics and applied mathematics
Broad outlines not specific details

6. Historic Overview 1800s 1856: Prof. Joseph Henry 1877: Lord Rayleigh
“Treatise on Acoustics Applied to Public Buildings”
1877: Lord Rayleigh
“The Theory of Sound”
1895: Wallace Clement Sabine
Fogg Art Museum,

7. Historic Overview Buildings
1870: Der Grosse Saal der Gesellschaft der Musikfreunde, Vienna
1879: Central Music Hall, Chicago
1887: Chicago Auditorium, Chicago
1888: Concertgebouw, Amsterdam
1900: Boston Symphony Hall, Boston
: None of note
1948: Royal Festival Hall, London
1961: Lincoln Center, New York

8. Historic Overview By the 1920s Precise measurements became possible
Individual design and fabrication
1920s+
Radio, television, amplified sound/music, motion pictures fostered greater demand for analysis/design

9. Historic Overview Today Research to improve conditions for
Industrial noise
Hearing risks
Construction noise
Public health

10. Acoustical Design

11. Architect’s Role Source Path Receiver
slight major design primarily interest
influence

12. Acoustical Design “Proper acoustical planning
eliminates many acoustical problems before they are built”
Lee Irvine

13. Acoustical Design Relationships
Site
Location
Orientation
Planning
Internal Layout

14. Site
Match site to application
Match application to site

15. Site
Factory:
Close to RR/Hwy
Seismic

16. Site
Rest Home:
Traffic Noise
Outdoor Use
Contact/Isolation

17. Site
Concert Hall:
Use building as isolator
Distance from noise

18. Location
Take advantage of distance/barriers
Distance

19. Location
Take advantage of distance/barriers
Natural or Man-made Berm

20. Location
Take advantage of distance/barriers
Acoustical Barriers

21. Location
Take advantage of distance/barriers
Building

22. Orientation
Orient Building for Acoustical Advantage
Playground
School

23. Orientation Orient Building for Acoustical Advantage
Parking Lot
Factory
Office
Note: Sound is 3-dimensional,
check overhead for
flight paths

24. Consider Acoustical Sensitivity of Activities
Planning
Consider Acoustical Sensitivity of Activities
Noisy Quiet
Barrier

25. Consider Acoustical Sensitivity of Activities
Planning
Consider Acoustical Sensitivity of Activities
Critical
Non-Critical
Noise

26. Internal Layout Each room has needs that can be met by room layout
I: p.116 F.5-12

27. Basic Acoustic Goals Provide adequate isolation
Provide appropriate acoustic environment
Provide appropriate internal function
Integrate 1-3 amongst themselves and into comprehensive architectural design

28. Acoustics Fundamentals

29. Sound
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

30. Noise
Any unwanted sound

31. Sound Propagation
Sound travels at different speeds through various media.
Media Speed (C)
Air: 1,130 fps
Water: 4,625 fps
Wood: 10,825 fps
Steel: 16,000 fps

32. Wavelength 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 λ

33. Sound Magnitude
Sound Power (P)
Sound Intensity (I)

34. Sound Power Energy radiating from a point source in space.
Expressed as watts
S: p. 740, F.17.9

35. Sound power distributed over an area
Sound Intensity
Sound power distributed over an area
I=P/A
I: sound (power) intensity, W/cm2
P: acoustic power, watts
A: area (cm2)

36. Level of sound relative to a base reference
Intensity Level
Level of sound relative to a base reference
“10 million million: one”
S: p. 740, T.17.2

37. Extreme range dictates the use of logarithms
Intensity 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

38. Intensity Level Scale Change
Changes are measured in decibels
scale change subjective loudness
3 dB barely perceptible
6 dB perceptible
7 dB clearly perceptible
Note: round off to nearest whole number

39. Intensity Level—The Math
If 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/ =I2/10-16
I1= I2=10-11

40. Intensity Level—The Math
If IL1=60 dB and IL2=50dB,
what is the total sound intensity?
2. Add together
I1+I2=1 x x 10-11
ITOT=11 x W/cm2

41. Intensity Level—The Math
If 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 )/10-16
ILTOT=10 (Log 11 + Log 105 )
ILTOT=10 ( ) = dB

42. Intensity Level Add two 60 dB sources ΔdB=0, add 3 db to higher
IL=60+3=63 dB
S: p. 743, F.17.11

43. Sound 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)

44. Perceived Sound Dominant frequencies affect sound perception
S: p. 737, F.17.8

45. Sound Meter—”A” Weighting
Sound meters that interpret human hearing use an “A” weighted scale
dB becomes dBA