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16 November 2012Acoustical Parameters (ISO 3382) 1 Acoustical parameters ISO 3382.

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Presentation on theme: "16 November 2012Acoustical Parameters (ISO 3382) 1 Acoustical parameters ISO 3382."— Presentation transcript:

1 16 November 2012Acoustical Parameters (ISO 3382) 1 Acoustical parameters ISO 3382

2 16 November 2012Acoustical Parameters (ISO 3382) 2 ISO 3382 acoustical parameters

3 16 November 2012Acoustical Parameters (ISO 3382) 3 From Impulse Response to Sound Decay Schroeders backward integral Makes it possible to reconstruct the decay of a stationary source by backward integration of the measured impulse response

4 16 November 2012Acoustical Parameters (ISO 3382) 4 Schroeders BW Integration Pressure Impulse Response Energetic Impulse Response (in dB) Stationary Sound Decay (in dB)

5 Reverberation time T20 Lp (dB) Time (s) 45 dB -5 dB -25 dB T November 2012Acoustical Parameters (ISO 3382) 5

6 16 November 2012Acoustical Parameters (ISO 3382) 6 ISO 3382 Reverberation Time(s) Early Decay Time (EDT): extrapolated from 0 to -10 dB Reverberation Time T 10 : extrapolated from -5 to -15 dB Reverberation Time T 20 : extrapolated from -5 to -25 dB Reverberation Time T 30 : extrapolated from -5 to -35 dB

7 16 November 2012Acoustical Parameters (ISO 3382) 7 Early – Late energy evaluation Useful EnergyDetrimental Energy

8 16 November 2012Acoustical Parameters (ISO 3382) 8 Early-Late parameters Clarity Index C 80 (symphonic music): Clarity Index C 50 (speech): Optimal Value = +/- 1 dB

9 16 November 2012Acoustical Parameters (ISO 3382) 9 Early-Late parameters Center Time t S : Definition Index D:

10 Other acoustical parameters Strenght: IACC: SPL at 10 m 16 November 2012Acoustical Parameters (ISO 3382) 10

11 16 November 2012Acoustical Parameters (ISO 3382) 11 Other acoustical parameters LFC: Lateral Fraction:

12 16 November 2012Acoustical Parameters (ISO 3382) 12 Spatial analysis by directive impulse responses The initial approach was to use directive microphones for gathering some information about the spatial properties of the sound field as perceived by the listener Two apparently different approaches emerged: binaural dummy heads and pressure-velocity microphones: Binaural microphone (left) and Pressure-velocity microphone (right)

13 16 November 2012Acoustical Parameters (ISO 3382) 13 IACC objective spatial parameter It was attempted to quantify the spatiality of a room by means ofobjective parameters, based on 2-channels impulse responses measured with directive microphones The most famous spatial parameter is IACC (Inter Aural Cross Correlation), based on binaural IR measurements Left Right 80 ms p L ( ) p R ( )

14 16 November 2012Acoustical Parameters (ISO 3382) 14 Lateral Fraction (LF) spatial parameter Another spatial parameter is the Lateral Fraction J LF This is defined from a 2-channels impulse response, the first channel is a standard omni microphone, the second channel is a figure-of-eight microphone: Figure of 8 Omni h o ( ) h 8 ( )

15 16 November 2012Acoustical Parameters (ISO 3382) 15 Are binaural measurents reproducible? Experiment performed in anechoic room - same loudspeaker, same source and receiver positions, 5 binaural dummy heads

16 Are IACC measurements reproducible? 90° incidence - at low frequency IACC is almost 1, at high frequency the difference between the heads becomes evident 16 November 2012Acoustical Parameters (ISO 3382) 16

17 16 November 2012Acoustical Parameters (ISO 3382) 17 Are IACC measurements reproducible? Diffuse field - huge difference among the 4 dummy heads

18 16 November 2012Acoustical Parameters (ISO 3382) 18 Are LF measurents reproducible? Experiment performed in the Auditorium of Parma - same loudspeaker, same source and receiver positions, 4 pressure-velocity microphones

19 At 7.5 m distance, the results already exhibit significant scatter Are LF measurents reproducible? 16 November 2012Acoustical Parameters (ISO 3382) 19

20 16 November 2012Acoustical Parameters (ISO 3382) 20 Are LF measurents reproducible? At 25 m distance, the scatter is even larger

21 16 November 2012Acoustical Parameters (ISO 3382) 21 The Aurora Acoustical Parameters plugin


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