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Room and Auditorium Acoustics

Room and Auditorium Acoustics. Criteria in Acoustical Design Problems in Acoustical Design Control of Reverberation Time Design of Auditoriums Home Listening Rooms. Paths of sound in room. Intensity vs. time for pulse. Average Intensity vs. Time. for a constant tone.

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Room and Auditorium Acoustics

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  1. Room and Auditorium Acoustics • Criteria in Acoustical Design • Problems in Acoustical Design • Control of Reverberation Time • Design of Auditoriums • Home Listening Rooms

  2. Paths of sound in room

  3. Intensity vs. time for pulse

  4. Average Intensity vs. Time for a constant tone

  5. Ideal Reverberation Times

  6. Acoustical Characteristics • Liveness • Intimacy • Fullness • Clarity • Warmth • Brilliance • Texture • Blend • Ensemble

  7. Liveness Measure of reverberation time Good or bad?

  8. Intimacy Room said to be “intimate” when the first reverberation arrives within 20 ms of the direct sound. Good or bad?

  9. Fullness vs. Clarity Refers to the amount of reflected sound relative to the amount of direct sound Good or bad?

  10. Warmth vs. Brilliance Warmth increases with increasing TR for low frequencies

  11. Texture “Good texture” when at least five reflections arrive within 60ms of direct sound

  12. Blend and Ensemble Ability to hear the entire performing group on the stage (ensemble) and in the audience (blend)

  13. Acoustical Design Problems • Focusing of sound • Echoes • Shadows • Resonances • External noise • Double-valued TR

  14. Focusing of Sound Occurs with use of parabolic surfaces either behind performers or at rear of auditorium

  15. Echoes Highly reflective flat or parabolic wall shapes Flutter echos from parallel walls Standing waves between parallel walls

  16. Resonances Parallel walls Rectangular practice rooms Singing in the shower

  17. External noise Box within a box construction Practice rooms and concert halls in adjacent areas

  18. Double-valued TR Playback room with reverberation Concert halls with side areas

  19. Auditorium Design

  20. General Design Considerations • Visual • Ventilation • Acoustical • a. seating • b. stage • c. room shape • d. room walls

  21. Control of TR TR = 0.050 V / A Where: TR = reverberation time in second V = room volume in cubic feet A = total room absorption in sabins

  22. TRCalculation A = a1A1 + a2A2 + a3A3 + a4A4 + … An is one section of absorbent area an is absorption coefficient TR = 0.050 V/A

  23. Some Absorption Coefficients Frequency (Hz) Material 125 250 500 1000 2000 4000 Concrete/brick 0.01 0.01 0.02 0.02 0.02 0.03 Glass 0.19 0.08 0.06 0.04 0.03 0.02 Plasterboard 0.20 0.15 0.10 0.08 0.04 0.02 Plywood 0.45 0.25 0.13 0.11 0.10 0.09 Carpet 0.10 0.20 0.30 0.35 0.50 0.60 Curtains 0.05 0.12 0.25 0.35 0.40 0.45 Acoustical board 0.25 0.45 0.80 0.90 0.90 0.90

  24. Absorptions (in sabins) Frequency (Hz) Material 125 250 500 1000 2000 Unupholstered seat 0.15 0.22 0.25 0.28 0.50 Upholstered seat 3.0 3.1 3.1 3.2 3.4 Adult person 2.5 3.5 4.2 4.6 5.0 Adult/upholstered seat 3.0 3.8 4.5 5.0 5.2

  25. Dekelbaum Concert Hallat the U MDSmith Center

  26. Dekelbaum Concert Hall (front)

  27. Dekelbaum Concert Hall (rear)

  28. Dekelbaum Concert Hall (top)

  29. U MD Tawes Recital Hall

  30. Microphone configuration in concert hall

  31. Loudspeaker configuration in home listening rooms

  32. The End

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