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Characterization of closed spaces,
ISO 3382-3
R.Narasimha Swamy
Senior consultant
narasimhaswamy@yahoo.com
Introduction
• RT60 - just a single number and is a classical
measure of acoustics characteristics of the closed
spaces.
•...
ISO-3382-3 (1997-E)
• ISO-3382 is a method suggested by ISO
organization for acoustic measurement of
the enclosed spaces.
...
ISO 3382 parameters
Description of
acoustic
parameter
Symbol Definition or expression
Proposed
by
Attributes
Reverberation...
5
ISO 3382 Reverberation Time(s)
 Early Decay Time (EDT): extrapolated from 0 to -10 dB
 Reverberation Time T10: extrapo...
Reverberation time T20
Lp
(dB)
Time (s)
45 dB
-5 dB
-25 dB
T20
7
Early – Late energy evaluation
Useful Energy Detrimental Energy
Early-Late parameters
 
  

















ms
ms
dττp
dττp
C
80
2
80
0
2
80 lg10
 Clarity Index C...
Early-Late parameters
 Center Time tS:
 
 






0
2
0
2


dp
dp
ts
 
 
100
dp
dp
D
0
2
ms50
0
2

...
Other acoustical parameters
• Strength: dB31LSPLG w 
 
   
   










dthdh
dt...
Room impulse response and
Schroeder decay function
determined from an
experimentally
measured room impulse
response in two...
Case studies of reverb and anechoic
chamber
Impulse response of reverberant room
Decay curve of reverberant room
Characteristics of reverberant room as per
ISO-4482
Impulse response of anechoic chamber
Decay curve of anechoic chamber
Characteristics of anechoic chamber as per ISO-4482
Importance of acoustics in learning
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Iso 3382 standards for acoustic measurements

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An important standard for characterization of acoustics of inner spaces. A must for acoustic.

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Iso 3382 standards for acoustic measurements

  1. 1. Characterization of closed spaces, ISO 3382-3 R.Narasimha Swamy Senior consultant narasimhaswamy@yahoo.com
  2. 2. Introduction • RT60 - just a single number and is a classical measure of acoustics characteristics of the closed spaces. • However, RT60 is not sufficient to completely characterize the enclosed spaces, as it does not consider several important characteristics like relative SPL, energy fraction of the early/late reflections, lateral reflections, background noise etc. • These factors are very important measure for spatial impression of auditoriums, speech intelligibility in class rooms, offices, multi purpose halls etc.
  3. 3. ISO-3382-3 (1997-E) • ISO-3382 is a method suggested by ISO organization for acoustic measurement of the enclosed spaces. • All the important characteristics like energy fraction of the early/late reflections, lateral reflections, background noise are derived from the Sabin’s classical sound decay characteristics.
  4. 4. ISO 3382 parameters Description of acoustic parameter Symbol Definition or expression Proposed by Attributes Reverberation RT60 (sec) Time taken for the sound in a room to decay to 60 dB below the source level, after the source is muted. Sabine 1923 Characterizes the enclosed space Early decay time EDT (S) Early Decay Time is the reverberation time, measured over the first 10 dB of the decay. Jordan, 1975 Provides subjective evaluation of the RT Clarity C50 Ratio Early to late arriving sound energy ratio Reichardt 1975 Acoustic clarity with reference to room size perception Definition D50 (%) The D50 parameter is the early to total sound energy ratio. It is defined as Thiele 1953 Speech intelligibility and sound definition Signal to noise ratio SNR (dB) Lchner e Burger, 1964 Speech intelligibility Rapid speech transmission index RASTI (ratio) [S/N media +15]/30 Steeneken e Houtgast 1980 Speech intelligibility
  5. 5. 5 ISO 3382 Reverberation Time(s)  Early Decay Time (EDT): extrapolated from 0 to -10 dB  Reverberation Time T10: extrapolated from -5 to -15 dB  Reverberation Time T20: extrapolated from -5 to -25 dB  Reverberation Time T30: extrapolated from -5 to -35 dB
  6. 6. Reverberation time T20 Lp (dB) Time (s) 45 dB -5 dB -25 dB T20
  7. 7. 7 Early – Late energy evaluation Useful Energy Detrimental Energy
  8. 8. Early-Late parameters                       ms ms dττp dττp C 80 2 80 0 2 80 lg10  Clarity Index C80 (symphonic music):  Clarity Index C50 (speech): Optimal Value = +/- 1 dB Optimal Value = +/- 1 dB                       ms ms dττp dττp C 80 2 50 0 2 50 lg10
  9. 9. Early-Late parameters  Center Time tS:           0 2 0 2   dp dp ts     100 dp dp D 0 2 ms50 0 2         Definition Index D:
  10. 10. Other acoustical parameters • Strength: dB31LSPLG w                      dthdh dthh t 2 s 2 d sd  IACC: SPL at 10 m IACC: Inter Aural Cross Correlation
  11. 11. Room impulse response and Schroeder decay function determined from an experimentally measured room impulse response in two coupled scaled- down model rooms. (a) Room impulse response octave band-pass filtered at 1kHz with peak-to-noise ratio equal to 53 dB. (b) Schroeder decay function.
  12. 12. Case studies of reverb and anechoic chamber
  13. 13. Impulse response of reverberant room
  14. 14. Decay curve of reverberant room
  15. 15. Characteristics of reverberant room as per ISO-4482
  16. 16. Impulse response of anechoic chamber
  17. 17. Decay curve of anechoic chamber
  18. 18. Characteristics of anechoic chamber as per ISO-4482
  19. 19. Importance of acoustics in learning
  20. 20. Thanks

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