1. 1AES tutorial, 2008 Small Room Acoustics Ben Kok Nelissen ingenieursbureau b.kok@nelissenbv.nl

2. 2AES tutorial, 2008 Introduction What is a sound wave?What is a sound wave?

3. 3AES tutorial, 2008 Sound wave

4. 4AES tutorial, 2008 Sound wave F = 100 Hz → λ = 3,4 m F = 1 kHz → λ = 0,34 m F = 10 kHz → λ = 0,034 m

5. 5AES tutorial, 2008 When do we consider a room ‘Small’?

6. 6AES tutorial, 2008 Small Rooms Living RoomLiving Room Recording StudioRecording Studio Control RoomControl Room CarCar Telephone BoothTelephone Booth HeadphoneHeadphone

7. 7AES tutorial, 2008 Low frequencies in an enclosure

8. 8AES tutorial, 2008 Low frequencies in an enclosure

9. 9AES tutorial, 2008 Low frequencies in an enclosure “Golden” ratios: ASHREA1:1.17:1.47 ASHREA1:1.45:2.10 Bolt1:1.28:1.54 IAC1:1.26:1.60 Seppmeyer1:1.14:1.39 Kok1:1.12:1.41

10. 10AES tutorial, 2008 Room mode analysis

11. 11AES tutorial, 2008 absorption porous materialporous material resonatorsresonators sandwich constructionssandwich constructions

12. 12AES tutorial, 2008 porous material

13. 13AES tutorial, 2008 porous material

14. 14AES tutorial, 2008 porous material

15. 15AES tutorial, 2008 porous material Rule of thumb:

16. 16AES tutorial, 2008 resonator

17. 17 diafragmatic resonator

18. 18AES tutorial, 2008 diafragmatic resonator flexible panels thinthin largelarge high internal losshigh internal loss excited over the full area

19. 19AES tutorial, 2008 Helmholtz resonator

20. 20AES tutorial, 2008 diffusion spatial and temporal distribution of energy

21. 21AES tutorial, 2008 Specular reflection

22. 22AES tutorial, 2008 Diffuse reflection 1

23. 23AES tutorial, 2008 Diffuse reflection 2

24. 24AES tutorial, 2008 diffuser example

25. 25AES tutorial, 2008 diffusion repetition of the same sequence should be avoided!! > grating lobes! > grating lobes!

26. 26AES tutorial, 2008 phase modulated array of diffusers

27. 27AES tutorial, 2008 installation example

28. 28AES tutorial, 2008 microphone/ loudspeaker placement early reflections (1 st 10 ms) cause colorationearly reflections (1 st 10 ms) cause coloration specular reflections (narrow peak) cause comb filteringspecular reflections (narrow peak) cause comb filtering diffuse reflections add ‘warmth’diffuse reflections add ‘warmth’

29. 29AES tutorial, 2008 microphone/ loudspeaker placement distant micing/ listening allows sound to developdistant micing/ listening allows sound to develop close micing/ listening minimizes room influenceclose micing/ listening minimizes room influence a small room has no statistic sound field, strong variation between positions can exista small room has no statistic sound field, strong variation between positions can exist

30. 30AES tutorial, 2008 microphone/ loudspeaker placement room modes have a significant influence on low frequency coupling; loudspeaker position can have a strong influence on low frequency responseroom modes have a significant influence on low frequency coupling; loudspeaker position can have a strong influence on low frequency response distributed sub-woofers can create a smoother low frequency responsedistributed sub-woofers can create a smoother low frequency response a small room has no statistic sound field, strong variation between positions can exista small room has no statistic sound field, strong variation between positions can exist

31. 31AES tutorial, 2008 conclusion a small room behaves different because it’s dimensions are similar to the wavelength of the (re)produced sounda small room behaves different because it’s dimensions are similar to the wavelength of the (re)produced sound source and listening positions often are fixed -> the design can accommodate for thissource and listening positions often are fixed -> the design can accommodate for this changing positions can have a dramatic influencechanging positions can have a dramatic influence

32. 32AES tutorial, 2008 QUESTIONS