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

ISO 3382 acoustical parameters 09/13/2003 ISO 3382 acoustical parameters 16 November 2012 Acoustical Parameters (ISO 3382) AES 115th Convention - New York, NY

From Impulse Response to Sound Decay 09/13/2003 From Impulse Response to Sound Decay Schroeder’s backward integral Makes it possible to reconstruct the decay of a stationary source by backward integration of the measured impulse response 16 November 2012 Acoustical Parameters (ISO 3382) AES 115th Convention - New York, NY

Schroeder’s BW Integration 09/13/2003 Schroeder’s BW Integration Pressure Impulse Response Stationary Sound Decay (in dB) Energetic Impulse Response (in dB) 16 November 2012 Acoustical Parameters (ISO 3382) AES 115th Convention - New York, NY

Acoustical Parameters (ISO 3382) Reverberation time T20 Lp (dB) -5 dB 45 dB -25 dB Time (s) T20 16 November 2012 Acoustical Parameters (ISO 3382)

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 16 November 2012 Acoustical Parameters (ISO 3382)

Early – Late energy evaluation 09/13/2003 Useful Energy Detrimental Energy 16 November 2012 Acoustical Parameters (ISO 3382) AES 115th Convention - New York, NY

Early-Late parameters Clarity Index C80 (symphonic music): Optimal Value = +/- 1 dB Clarity Index C50 (speech): Optimal Value = +/- 1 dB 16 November 2012 Acoustical Parameters (ISO 3382)

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

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

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

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) 16 November 2012 Acoustical Parameters (ISO 3382)

IACC “objective” spatial parameter It was attempted to “quantify” the “spatiality” of a room by means of “objective” 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 pL(t) Right pR(t) 80 ms 16 November 2012 Acoustical Parameters (ISO 3382)

Lateral Fraction (LF) spatial parameter Another “spatial” parameter is the Lateral Fraction JLF 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: Omni ho(t) Figure of 8 h8(t) 16 November 2012 Acoustical Parameters (ISO 3382)

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

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 2012 Acoustical Parameters (ISO 3382)

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

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

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

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

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