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Technology in Architecture

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

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Technology in Architecture

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  1. Technology in Architecture Lecture 16 Historic Overview Acoustical Design Sound in Enclosed Spaces Reverberation

  2. Historic Overview Greek Theatre • Open air • Direct sound path • No sound reinforcement • Minimal reverberation S: p. 785, F.18.17a

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

  4. Acoustical Design—Architect’s Role Source Path Receiver slight major design primarily interest influence

  5. Acoustical Design Relationships Site Location Orientation Planning Internal Layout

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

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

  8. Location Take advantage of distance/barriers Distance

  9. Location Take advantage of distance/barriers Acoustical Barriers

  10. Orientation Orient Building for Acoustical Advantage Playground School Note: Sound is 3-dimensional, check overhead for flight paths

  11. Planning Consider Acoustical Sensitivity of Activities Noisy Quiet Barrier

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

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

  14. Acoustical Fundamentals—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

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

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

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

  18. 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

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

  24. 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)

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

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

  27. Sound In Enclosed Spaces—Sound Absorption Amount of sound energy not reflected S: p. 771, , F.18.2

  28. Sound Absorption Absorption 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

  29. Sound Absorption Absorption coefficient S: p. 769, T.18.1

  30. Sound Absorption Absorption A=Sα A=total absorption (sabins) S=surface area (ft2 or m2) α=absorption coefficient sabins (m2)= 10.76 sabins (sf)

  31. Sound Absorption Total Absorption Σα=S1α1+ S2α2+ S3α3+…+Snαn or ΣA=A1+ A2+ A3+…+An

  32. Sound Absorption Average Absorption αavg=ΣA/S αavg <0.2 “live” αavg >0.4 “dead” S: p. 774, F.18.6

  33. Reflection in enclosed spaces Acoustical phenomena S: p. 787, F.18.20 S: p. 788, F.18.21

  34. Ray diagrams Trace the reflection paths to and from adjoining surfaces angle of incidence = angle of reflection I R

  35. Ray 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

  36. Reflection inenclosed spaces Auditorium sound reinforcement S: p. 789, F.18.23

  37. Reverberation Persistence of sound after source has ceased S: p. 771, F.18.2

  38. Reverberation 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)

  39. ft3x1000 3.5 35.0 350 Reverberation Time Application Volume S: p. 782, F.18.13

  40. Reverberation Example Compile data • Material Absorption Coefficient • Material Surface Area SR-6: p.121

  41. ft3x1000 3.5 35.0 350 Reverberation Example Compare to requirements and adjust S: p. 782, F.27.13

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