1A.Diederich– International University Bremen – USC – MMM – Spring 2005

Onset and offset

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

2A.Diederich– International University Bremen – USC – MMM – Spring 2005

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.

3A.Diederich– International University Bremen – USC – MMM – Spring 2005

– 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.

4A.Diederich– International University Bremen – USC – MMM – Spring 2005

– 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).

5A.Diederich– International University Bremen – USC – MMM – Spring 2005

Location

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

6A.Diederich– International University Bremen – USC – MMM – Spring 2005

Sound localization

– Goldstein, pp. 375 – 385

7A.Diederich– International University Bremen – USC – MMM – Spring 2005

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.

8A.Diederich– International University Bremen – USC – MMM – Spring 2005

1. The azimuth (horizontal) coordinate specifies localizations that vary from left to right (right to left) relative to the listener

2. The elevation (vertical) coordinate specifies localization that are up and down relative to the listener

3. The distance coordinate specifies how far the sound source is from the listener

9A.Diederich– International University Bremen – USC – MMM – Spring 2005

Information for azimuth

Interaural time difference

Interaural level difference

Phase difference

10A.Diederich– International University Bremen – USC – MMM – Spring 2005

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.

11A.Diederich– International University Bremen – USC – MMM – Spring 2005

Maximal difference:600 s

Difference threshold:10 s

The principle behind interaural time difference

12A.Diederich– International University Bremen – USC – MMM – Spring 2005

Cone of confusion

The difference in pathlength between the stimulus and the listener’s two ears is the same everywhere on the surface of this cone.The timing differences betweenthe ears therefore remains thesame, and, assuming that thehead is perfectly spherical, theintensity differences do notchange either. Solution: Move your head

13A.Diederich– International University Bremen – USC – MMM – Spring 2005

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.

14A.Diederich– International University Bremen – USC – MMM – Spring 2005

The principle behind interaural level difference

Low-frequency tones arenot affected by the listener's head

High-frequency tones are affected by the presenceof the listener's head, andthe result is an acoustic"shadow" that decreasesthe intensity of the tonereaching the listener'sfar ear.

15A.Diederich– International University Bremen – USC – MMM – Spring 2005

70 dB SPL 2 m from center of head

– 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.

16A.Diederich– International University Bremen – USC – MMM – Spring 2005

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.

17A.Diederich– International University Bremen – USC – MMM – Spring 2005

Information for Elevation

Spectral cues (Head related transfer function; HRTF):The difference between the sound from the source and the sound actually enteringthe ears.

The head and pinnae

decreases the intensity

of some frequencies

and enhance others.

Sound presented at three different locations

18A.Diederich– International University Bremen – USC – MMM – Spring 2005

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

19A.Diederich– International University Bremen – USC – MMM – Spring 2005

Precedence effect

20A.Diederich– International University Bremen – USC – MMM – Spring 2005

Fusion

Precedence effect Echo

21A.Diederich– International University Bremen – USC – MMM – Spring 2005

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.

22A.Diederich– International University Bremen – USC – MMM – Spring 2005

Auditory scene

23A.Diederich– International University Bremen – USC – MMM – Spring 2005

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.

24A.Diederich– International University Bremen – USC – MMM – Spring 2005

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.

25A.Diederich– International University Bremen – USC – MMM – Spring 2005

– 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

26A.Diederich– International University Bremen – USC – MMM – Spring 2005

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 .

27A.Diederich– International University Bremen – USC – MMM – Spring 2005

Chromatic illusion

28A.Diederich– International University Bremen – USC – MMM – Spring 2005

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

29A.Diederich– International University Bremen – USC – MMM – Spring 2005

Such effects occur when listening to live music in concert halls

Tchaikokvsky's Sixth Symphony(The Pathetique)Even true with the orchestraarranged in 19th century fashion

Rachmaninoff's Second Suite forTwo Pianos

30A.Diederich– International University Bremen – USC – MMM – Spring 2005

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.

31A.Diederich– International University Bremen – USC – MMM – Spring 2005

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.

32A.Diederich– International University Bremen – USC – MMM – Spring 2005

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

33A.Diederich– International University Bremen – USC – MMM – Spring 2005

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

34A.Diederich– International University Bremen – USC – MMM – Spring 2005

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

35A.Diederich– International University Bremen – USC – MMM – Spring 2005

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