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Small Room Acoustics

Small Room Acoustics. Ben Kok Nelissen ingenieursbureau b.kok@nelissenbv.nl. Introduction. What is a sound wave?. Sound wave. Sound wave. F = 100 Hz → λ = 3,4 m F = 1 kHz → λ = 0,34 m F = 10 kHz → λ = 0,034 m. When do we consider a room ‘Small’?. Small Rooms. Living Room

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Small Room Acoustics

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

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

  3. Sound wave AES tutorial, 2008

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

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

  6. Small Rooms • Living Room • Recording Studio • Control Room • Car • Telephone Booth • Headphone AES tutorial, 2008

  7. Low frequencies in an enclosure AES tutorial, 2008

  8. Low frequencies in an enclosure AES tutorial, 2008

  9. Low frequencies in an enclosure “Golden” ratios: ASHREA 1:1.17:1.47 ASHREA 1:1.45:2.10 Bolt 1:1.28:1.54 IAC 1:1.26:1.60 Seppmeyer 1:1.14:1.39 Kok 1:1.12:1.41 AES tutorial, 2008

  10. Room mode analysis AES tutorial, 2008

  11. absorption • porous material • resonators • sandwichconstructions AES tutorial, 2008

  12. porous material AES tutorial, 2008

  13. porous material AES tutorial, 2008

  14. porous material AES tutorial, 2008

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

  16. resonator AES tutorial, 2008

  17. diafragmatic resonator AES tutorial, 2008

  18. diafragmatic resonator • flexible panels • thin • large • high internal loss • excited over the fullarea AES tutorial, 2008

  19. Helmholtz resonator AES tutorial, 2008

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

  21. Specular reflection AES tutorial, 2008

  22. Diffuse reflection 1 AES tutorial, 2008

  23. Diffuse reflection 2 AES tutorial, 2008

  24. diffuser example AES tutorial, 2008

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

  26. phase modulated array of diffusers AES tutorial, 2008

  27. installation example AES tutorial, 2008

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

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

  30. microphone/ loudspeaker placement • room 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 response • a small room has no statistic sound field, strong variation between positions can exist AES tutorial, 2008

  31. conclusion • a 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 this • changing positions can have a dramatic influence AES tutorial, 2008

  32. QUESTIONS AES tutorial, 2008

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