Onset and offset

1. Onset and offset Sounds that stop and start at different times tend to be produced by different sources.

2. Onset asynchrony have also higher level effects • Listeners were presented with a two-tone complex in alternation with a third tone. Bregman and Pinker (1978) studied the effects of onset-offset asynchrony between the simultaneous tones. • As the degree of onset asynchrony increased, the timbre of the complex tone was judged to be purer, and it became more probable that one of the tones in the complex would form a melodic stream with the third one.

3. When two complex tones are played together, they are perceptually more distinct when their onsets are asynchronous than when they begin to sound at the same time. • Larger amounts of asynchrony should produce even better and more reliable separation of voices.

4. Hypothesis: Compositional practice would exploit this effect – at least in polyphonic music where it is intended that the individual voices should be distinctively heard. • An analysis of J.S.Bach's 15 two-part inventions showed this for 11 of these inventions (Huron, 1993).

5. Location Sounds created by a particular source usually come from one position in space or from a slowly changing location.

6. Sound localization • Goldstein, pp. 375 – 385

7. Sound localization • Participant's ability to localize sound. • The asterisks are the actual sound locations, and the circles are the participant's estimates of their location. • Longer lines connecting the asterisks and circles indicate less accurate locations.

8. The azimuth (horizontal) coordinate specifies localizations that vary from left to right (right to left) relative to the listener • The elevation (vertical) coordinate specifies localization that are up and down relative to the listener • The distance coordinate specifies how far the sound source is from the listener

9. Information for azimuth Interaural time difference Interaural level difference Phase difference

10. Interaural time differences The difference between the time taken by the sound to travel to the two ears when starting from azimuth other than 0 and 180 degrees; a cue to the direction of a lower-frequency sound source.

11. The principle behind interaural time difference Maximal difference: 600 s Difference threshold: 10 s

12. Cone of confusion The difference in path length between the stimulus and the listener’s two ears is the same everywhere on the surface of this cone. The timing differences between the ears therefore remains the same, and, assuming that the head is perfectly spherical, the intensity differences do not change either. Solution: Move your head

13. Interaural intensity (sound pressure level) difference A difference in sound intensity at the two ears caused by the presence of a sound shadow (created by the head); cue to localization of higher-frequency sounds.

14. The principle behind interaural level difference Low-frequency tones are not affected by the listener's head High-frequency tones are affected by the presence of the listener's head, and the result is an acoustic "shadow" that decreases the intensity of the tone reaching the listener's far ear.

15. The difference in intensity between the two ears for a 70 dB SPL tone of different frequencies located ate different places around the head. • The tones were located 2m from the center of the head. 2 m from center of head 70 dB SPL

16. Phase difference The difference in the phase of a sound wave between the two ears caused by the different distances the sound wave has to travel to reach each ear; cue to localization of lower-frequency sounds.

17. Information for Elevation Sound presented at three different locations The head and pinnae decreases the intensity of some frequencies and enhance others. • Spectral cues (Head related transfer function; HRTF): • The difference between the sound from the source and the sound actually entering • the ears.

18. The auditory system does not use localization cues as primary basis for grouping, but instead uses them only when other supporting cues are present.

19. Precedence effect

20. Fusion Echo Precedence effect

21. Experience • Interleaved melodies (see above) • When participants were told the names of the songs, they were able to hear the melody to which they were paying attention.

22. Auditory scene

23. Grouping of multiple tone sequences in space • Do we form linkages between tones that are similar in pitch, loudness, or in timbre? • Alternatively, do we invoke spatial location as a prominent grouping cue? • All these factors are involved in grouping, but they interact in complex ways.

24. Scale illusion or melodic channeling The participants listened to the scales through earphones that presented successive notes from a major scale with successive tones alternating from ear to ear. The scale is played simultaneously in both ascending and descending form. The sequence is played repeatedly without pause.

25. A melody corresponding to the higher tones is heard as coming from one ear (in right-handers, generally the one on the right), with a melody corresponding to the lower tones as coming from the other earphone. • Earphone positions reversed ! apparent locations of the higher and lower tones often remain fixed

26. Grouping by pitch proximity is so powerful that not only are the tones organized melodically in accordance with this principle, but they are frequently reorganized in space to conform with this principle also .

27. Chromatic illusion

28. Variation of the experiment • loudspeakers • differences in timbre • Moderate differences in timbre did not alter the basic effect (new tone quality was heard, but it appeared to be coming simultaneously from both speakers). • Substantial differences in timbre (e.g., piano, saxophone) ! timbre was used as a basis for grouping

29. Such effects occur when listening to live music in concert halls Rachmaninoff's Second Suite for Two Pianos Tchaikokvsky's Sixth Symphony (The Pathetique) Even true with the orchestra arranged in 19th century fashion

30. The perceptual tendency to form melodic streams based on overall pitch range is reflected in the avoidance of part crossing in polyphonic music, e.g., Bach.

31. What happens when temporal disparities are introduced? • When the tones arrive at the two ears simultaneously they are organized sequentially on the basis of pitch proximity. • When the tones at the two ears are clearly separated in time they are grouped on the basis of spatial location.

32. High tones – right-handedness • Musically trained participants were presented with simultaneous sequences, one to each ear, and they transcribed them to musical notation. • high-right/low-left chords; low-right/high-left/chords • Notate the tones that were presented to one ear, ignore those presented to the other

33. Result • Attention to right ear • more higher than lower tones were notated correctly • more higher tones than lower ones intruded from the left ear into their notation • Attention to left ear • notated correctly virtually the same number of higher and of lower tones, with a marginal advantage to the lower ones • more lower tones than higher ones intruded from the right ear into their notations

34. Seating plan for the Chicago Symphony, as viewed from the orchestra

35. Paradox • From the performer's point of view, instruments with higher registers are to the right and those with lower registers are to the left • From the audience's point of view, instruments with higher registers tend to be to the left, and those with lower registers, to the right. • Instruments with low registers, which are to the audience's right, should be less well perceived and localized. • No solution to the problem