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Loudness: Current Knowledge and Questions

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Loudness: Current Knowledge and Questions ITU-T Workshop on "From Speech to Audio: bandwidth extension, binaural perception" Lannion, France, 10-12 September 2008 Loudness: Current Knowledge and Questions Sabine Meunier, Laboratoire de Mécanique et d’Acoustique – CNRS - France International Telecommunication Lannion, France, 10-12 September 2008 Union Loudness Supraliminary sensation: how to measure it ? Weber-Fechner law, 19th century Weber: ΔΦ/Φ=constant Φ:stimulation Fechner:ΔΨ=k ΔΦ/ΦΨ: sensation Ψ = A LogΦ + B Stevens law: direct measurement, magnitude estimation b Ψ = a Φ International Telecommunication Union 2 Lannion, France, 10-12 September 2008 Methods to measure Loudness Magnitude estimation: loudness in sones 1 sone = loudness of a 1-kHz tone at 40 dB SPL Adjustement (loudness matches): loudness level in phons a loudness level of a sound of X phons means that the sound is as loud as a 1-kHz tone at X dB SPL Adaptive (2down–1up, 1down–2up): loudness level in phons Multitracking: loudness level in phons Categorical loudness scaling International Telecommunication Union 3 Lannion, France, 10-12 September 2008 Methods to measure Loudness Adjustment Test sound (T): the sound that we want to know the loudness Sound of comparison (C): usually 1-kHz tone, variable level C after T (1st test) and T after C (2nd test) Listener’s task: Adjust the C-level to have the same loudness as T Random order, different for each listener Start level was randomly X dB above or under T loudness level International Loudness level in phons : mean of C-level obtainedTelecommunication in Union 4 Lannion,the France, 2 tests 10-12 September for 2008each sound Methods to measure Loudness Magnitude estimation: loudness in sones 1 sone = loudness of a 1-kHz tone at 40 dB SPL Adjustement (loudness matches): loudness level in phons a loudness level of a sound of X phons means that the sound is as loud as a 1-kHz tone at X dB SPL Adaptive (adown–bup, bdown–aup): loudness level in phons Multitracking: loudness level in phons Categorical loudness scaling International Telecommunication Union 5 Lannion, France, 10-12 September 2008 Methods to measure Loudness adaptive methods Presentation order : T & C or C & T, randomly 2down-1up (1st test) : Listener’s task : Which of these 2 sounds is louder Start level above the T loudness level ++ -5 dB 2nd reversal Mean of the last Y reversals ++ ++ -5 dB -2 dB --+5 dB + JL 1st reversal Track finishes after X reversals Loudness 2up-1down (2nd test) : level in phons 1st reversal ++ +5 dB +2 dB - JS -- -5 dB -- +5 dB 2nd reversal International -- Telecommunication Start level under the T loudness level Union 6 Lannion, France, 10-12 September 2008 Methods to measure Loudness Magnitude estimation: loudness in sones 1 sone = loudness of a 1-kHz tone at 40 dB SPL Adjustement (loudness matches): loudness level in phons a loudness level of a sound of X phons means that the sound is as loud as a 1-kHz tone at X dB SPL Adaptive (2down–1up, 1down–2up): loudness level in phons Multitracking: loudness level in phons Categorical loudness scaling International Telecommunication Union 7 Lannion, France, 10-12 September 2008 Methods to measure Loudness Multitracking Principle similar to the adaptive method 4 or 5 simultaneous sequences Random choice of the sequence, different for each listener Loudness level in phons: mean of +JL and –JS for each sound International Telecommunication Union 8 Lannion, France, 10-12 September 2008 Methods to measure Loudness Magnitude estimation: loudness in sones 1 sone = loudness of a 1-kHz tone at 40 dB SPL Adjustement (loudness matches): loudness level in phons a loudness level of a sound of X phons means that the sound is as loud as a 1-kHz tone at X dB SPL Adaptive (2down–1up, 1down–2up): loudness level in phons Multitracking: loudness level in phons Categorical loudness scaling International Telecommunication Union 9 Lannion, France, 10-12 September 2008 Methods to measure Loudness Categorical loudness scaling 50 too loud Loudness measured in 45 very loud Categorical Unit (CU) 40 35 loud 30 25 medium 20 15 soft 10 5 very soft 0 inaudible International Telecommunication Union 10 Lannion, France, 10-12 September 2008 Loudness as a function of SPL a 200 N=k(P-P0) 100 50 at 1 kHz: a=0.6 20 10 N: loudness 5.0 8000 Hz P: pressure 2.0 4000 Hz P0: constant 1.0 0.5 0.2 1000 Hz Loudness in sones 0.1 100 Hz .05 z 250 Hz H 0 .02 0 5 0 20 40 60 80 100 120 From Scharf (1978)International in Telecommunication Sound pressure level (dB) Handbook of perception,Union 11 Lannion, France, 10-12 September 2008 Carterette and Friedman Loudness as a function of SPL Partial loudness 50 20 10 5.0 2.0 1.0 Loudness in sones 0.5 0.2 Quiet 50 60 70 80 90 100 dB SPL of Noise 0.1 20 30 40 50 60 70 80 90 100 110 From Scharf International(1978) in SPL of masked tone (dB) Handbook ofTelecommunication perception, Union 12 Lannion, France, 10-12 September 2008 Carterette and Friedman Loudness as a function of frequency Equal loudness contours Standard: ISO 226, 2003 sound pressure level (dB) International frequency (Hz) Telecommunication Union 13 Lannion, France, 10-12 September 2008 Loudness as a function of frequency Equal loudness contours 90 ISO226 2003 ISO226 1987 80 75 phons 70 60 phons 60 50 phons 50 Sound Pressure Level (dB) Pressure Sound From Boullet (2005) 40 PhD Thesis 100 1000 10000 International Telecommunication Frequency (Hz) Union 14 Lannion, France, 10-12 September 2008 Loudness as a function of bandwidth Spectral loudness summation overall sound presure level From Scharf (1978) in Handbook of perception, critical band Carterette and Friedman Loudness level in phons International Telecommunication Bandwidth (Hz) Union 15 Lannion, France, 10-12 September 2008 Loudness as a function of duration Temporal loudness summation 72 1-kHz pure tone 70 68 66 64 62 60 y = 71.2+10*log(1-exp(-x/0,127)) Loudness level (phons) R² = 0,93 58 τ = 127 ms From Boullet (2005) Critical duration = 381 ms PhD Thesis 56 0,01 0,1 1 International Telecommunication Duration (s) Union 16 Lannion, France, 10-12 September 2008 Loudness models Standards for steady sounds ISO 532B, « Method for calculating loudness level », International Organisation for standardization (1975). From Zwicker E., Acustica, 10, 304 (1960) Zwicker E., J. Acoust. Soc. Am., 33, 248 (1961) ANSI, S3.4-2005, « Procedure for the Computation of Loudness of Steady Sounds, », American National Standards Institute, New York (2005). From Moore B. C. J. and Glasberg B. R., Acustica-Acta Acustica, 82, 335 (1996). Moore B. C. J., Glasberg B. R., Baer T., J. Audio Eng. Soc., 45, 224 (1997). International Telecommunication Union 17 Lannion, France, 10-12 September 2008 Zwicker’s model Stationary sounds, free or diffuse field Signal FFT a0 filtering From free field to inner ear aD+ filtering From free field to diffuse field Critical bands or 1/3 octave bands 1 24 Excitation Calculated using masking curves Specific loudness Based on Stevens law =Σ specific loudnesses Overall loudness International Telecommunication (because of spectral loudness summation)Union 18 Lannion, France, 10-12 September 2008 Moore and Glasberg’s model Stationary sounds, free or diffuse field Based on Zwicker’s model Differences: 1 –Auditory filters shapes, 2 –Excitation pattern, 3 - a0 and aD+ International Telecommunication Union 19 Lannion, France, 10-12 September 2008 Loudness models for non- stationary sounds Zwicker E., “Procedure for calculating loudness of temporally variable sounds”, J. Acoust. Soc. Am., vol.62, n°3, 675-682, 1977. Zwicker E. et Fastl H., “Psychoacoustics: Facts and models”, 2nd Edit ion, Springer-Verlag, Berlin, 1999. Glasberg B. R. and Moore B. C. J., “ A model of loudness applicable to time-varying sounds”, J. Audio Eng. Soc., 50, n°5, 331-342, 2002. International Telecommunication Union 20 Lannion, France, 10-12 September 2008 Current researches Loudness of non-stationary sounds Short duration signals Long duration signals Effect of context Induce Loudness Reduction (Recalibration) Loudness Constancy Binaural Loudness Summation Spectral loudness summation and duration International Telecommunication Union 21 Lannion, France, 10-12 September 2008 Loudness of non-stationary sounds Short duration sounds 20 Temporal integration = Lshort –Llong ) indB long 15 short and long signal at -L equal loudness short Temporal integration 10 depends on level Temporal integration maximum for moderate 5 Short varied levels Long varied Level Difference (L Difference Level 0 20 40 60 80 100 120 Level of Short Tone in dB SPL International Telecommunication Union 22 Lannion, France, 10-12 September 2008 From Florentine et al., JASA 1996 Loudness of non-stationary sounds Short duration sounds Loudness functions are not linear Modified Power Function 200-ms Equal-Ratio Loudness 20 5-ms Equal-Ratio Loudness ) in dB long 15 -L short 10 Lshort –Llong =14dB 5 Short varied Long varied Lshort –Llong =19dB Level Difference (L 0 20 40 60 80 100 120 International Level of Short Tone in dB SPL Telecommunication Union 23 Lannion, France, 10-12 September 2008 From Florentine et al., JASA 1996 Loudness of non-stationary sounds Short duration sounds These loudness functions show features similar to the mechanical input/output measurement at the basilar membrane Temporal integration of loudness does not depends on level International Telecommunication Union 24 Lannion, France, 10-12 September 2008 Loudness of non-stationary sounds Environmental short-duration sounds Most studies: Environmental sounds: Rectangular
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