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Technology in Architecture

Technology in Architecture. Lecture 16 Acoustics—Historical Overview Acoustical Design Acoustics Fundamentals. Historic Overview. Historic Overview. Greek Theatre Open air Direct sound path No sound reinforcement Minimal reverberation. S: p. 785, F.18.17a. Historic Overview.

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Technology in Architecture

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  1. Technology in Architecture Lecture 16 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. 785, F.18.17a

  4. Historic Overview 1st Century AD Vitruvius: “10 Books of Architecture” Sound reinforcement Reverberation S: p. 785, F.18.17b

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

  6. Acoustical Design

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

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

  9. Acoustical Design Relationships Site Location Orientation Planning Internal Layout

  10. Site Match site to application Match application to site

  11. Site Factory: • Close to RR/Hwy • Seismic

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

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

  14. Location Take advantage of distance/barriers Distance

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

  16. Location Take advantage of distance/barriers Acoustical Barriers

  17. Location Take advantage of distance/barriers Building

  18. Orientation Orient Building for Acoustical Advantage Playground School

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

  20. Planning Consider Acoustical Sensitivity of Activities Noisy Quiet Barrier

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

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

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

  24. Acoustics Fundamentals

  25. 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

  26. Noise Any unwanted sound

  27. 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

  28. 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

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

  30. Sound Power Energy radiating from a point source in space. Expressed as watts S: p. 750, F.17.9

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

  32. Intensity Level Level of sound relative to a base reference “10 million million: one” S: p. 750, T.17.2

  33. 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

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

  35. 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=I1/10-16 105=I2/10-16 I1=10-10 I2=10-11

  36. Intensity Level—The Math If 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

  37. 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 10-11 )/10-16 ILTOT=10 (Log 11 + Log 105 ) ILTOT=10 (1.04 +5) = 60.4 dB

  38. Intensity Level Add two 60 dB sources ΔdB=0, add 3 db to higher IL=60+3=63 dB S: p. 753, F.17.11

  39. 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)

  40. Perceived Sound Dominant frequencies affect sound perception S: p. 747, F.17.8

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

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