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. increasing TR for low frequencies
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. Practice rooms and concert halls
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. TR Calculation TR = 0.050 V/A A = a1A1 + a2A2 + a3A3 + a4A4 + …
An is one section of absorbent area
an is absorption coefficient
TR = V/A

23. Some Absorption Coefficients
Frequency (Hz)
Material
Concrete/brick
Glass
Plasterboard
Plywood
Carpet
Curtains
Acoustical board

24. Absorptions (in sabins)
Frequency (Hz)
Material
Unupholstered seat
Upholstered seat
Adult person
Adult/upholstered seat

25. Dekelbaum Concert Hall at the U MD Smith 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