Effects of reverberation on loudness perception

1. Effects of reverberation on loudness perception Andrew Raimond

2. Overview • Previous Experiments • Pilot; Real-room reverberation; Mono v Dichotic. • Current Experiments • Time order effects • Effects of frequency bands

3. Loudness asymmetry Attack Decay Ramped Sound Amplitude Damped Decay Attack Ramped Damped Sound Time

4. Loudness context effect Time • Which is loudest? Damped Damped Ramped Ramped Damped Ramped Ramped Damped

5. Reverberation • The “tails” on damped stimuli resemble effects of room reflections (Stecker & Hafter, 2000; Watkins, 2005). Dry speech Dry Speech Reverberated speech Reverberant Speech

6. Loudness judgement

7. Questions • Perceived reduction in loudness of damped stimuli relative to ramped stimuli • is this still apparent with sounds that have tails processed from real-room reflections? • The loudness context effect • is this still apparent with sounds that have tails processed from real-room reflections?

8. Real-room reverberation • However, tails added by real-room reverberation differ from the envelopes used by Stecker & Hafter: - Real-room decays are not smooth - Durations of real-room decays are usually longer - Room-reflections de-correlate the signal at the two ears Left Channel Right Channel

9. Experiment 1: Real-room • Can real-room reverberation over-ride artificial shaping used by Stecker & Hafter? • Perceived reduction in loudness of damped stimuli relative to ramped stimuli? • The loudness context effect? • Loudness asymmetry • Loudness context effect • Convolution with real-room reverberation overrides shaping used by Stecker & Hafter. • Effects of real-room reflections are more substantial than shaping used by Stecker & Hafter

10. Experiment 2: Monaural v Dichotic • Certain room-reflection ‘tail effects’ that have been found in speech perception experiments are increased in monaural conditions (Watkins, 2005). • Is the loudness context effect also increased when sounds are presented in monaural real-room reverberation? • Loudness asymmetry • Loudness context effect • Effects of the real-room tails successfully oppose effects of the function-shaped tails, as there was a substantial context effect that depended on the direction of the real-room tail. • As with ‘tail effects’ in speech, this context effect is found in both monaural and dichotic conditions, but is less prominent in dichotic conditions . • There appears to be a ‘de-reverberation’ in dichotic conditions that may be due to the de-correlation between the two ears’ signals with the real-room BRIRs

11. Experiment 3: Time order effects 500 ms ISI 1700 ms Damped-Ramped (Loudest) 1350 ms Damped-Damped (Least loud) 1350 ms Ramped-Ramped 1000 ms Ramped-Damped Time

12. Experiment3: Time order effects Damped- Ramped 500 ms Peak-to-Peak 1700 ms Damped- Damped 850 ms Ramped- Ramped 850 ms 850 ms Ramped- Damped 1200 ms

13. Experiment 3: Time order effects • 2IC task. • Pure tones of equal power (330 Hz, 250 ms). • Gated with either Ramped or Damped envelope, convolved with real-room 2.5 m BRIRs. • Played through left channel. • Standard stimulus (80 dB SPL), then ISI of 500,850,1200 or 1550 ms • Then Test stimulus (selected at random from 70,72,.., 90 dB SPL) • Which is loudest?

14. Experiment 3: Results 500 ms ISI Damped Standard Ramped Standard Ramped Test 1 Damped Test .5 Proportion Test > Standard responses 0 70 74 78 82 86 90 70 74 78 82 86 90 P.S.E P.S.E Test level (dB SPL) 14

15. Experiment 3: Results Damped Standard Ramped Standard 70 70 74 74 78 78 82 82 86 86 90 90 850 ms ISI Ramped Test 1 Damped Test .5 Proportion Test > Standard responses 0 P.S.E P.S.E Test level (dB SPL) 15

16. Experiment 3: Results Damped Standard Ramped Standard 70 70 74 74 78 78 82 82 86 86 90 90 1200 ms ISI Ramped Test 1 Damped Test .5 Proportion Test > Standard responses 0 P.S.E P.S.E Test level (dB SPL) 16

17. Experiment 3: Results Damped Standard Ramped Standard 70 70 74 74 78 78 82 82 86 86 90 90 1550 ms ISI Ramped Test 1 Damped Test .5 Proportion Test > Standard responses 0 P.S.E P.S.E Test level (dB SPL) 17

18. Experiment 3: Pooled Results 0.9 0.9 0.7 0.7 0.5 0.5 0.3 0.3 500 ms ISI 850 ms ISI Ramped Test Damped Test Total Proportion Test > Standard Responses Ramped Damped Ramped Damped Standard Type 18

19. Experiment 3: Pooled Results 0.9 0.9 0.7 0.7 0.5 0.5 0.3 0.3 1200msISI 1550msISI Ramped Test Damped Test Total Proportion Test > Standard Responses Ramped Damped Ramped Damped Standard Type 19

20. Experiment 3: Results 70 70 74 74 78 78 82 82 86 86 90 90 Equal Peak-to-Peak Times Ramped Standard Damped Standard 1 Ramp test 500 ms ISI Ramp test 850ms ISI .5 Proportion Test > Standard responses Damp test 850 ms ISI Damp test 1200ms ISI 0 P.S.E P.S.E Test level (dB SPL) 20

21. Experiment 3: Conclusions • Loudness asymmetry and loudness context effect are not dependant on Peak-to-Peak distance. • While still able to make loudness judgments, loudness asymmetry disappears with ISIs longer than 850 ms.Thus, loudness context effect does so too. • However, standard only contains one 300 ms reverberant tail, in one frequency region. Wideband (speech) contexts contain many more reverberant tails. 21

22. Experiment 4: • Ongoing experiments: Effects of frequency bands

23. Experiment 4: Effects of frequency bands • Perceptual constancy for reverberation is more effective within wideband sounds (Watkins & Makin, 2007). • Perceptual mechanism seems to operate on a band-by-band basis. • Test and standards used in Stecker & Hafter and in previous experiments have all occupied the same narrowband frequency region (300-Hz). • Use standards and test sounds in different frequency bands to examine loudness asymmetry • Investigate if loudness context effects are still apparent with cross-band standards and test sounds.

24. Thanks Thank you!