pitch perception - arizona state...

Pitch PerceptionRoger Shepard

Tuesday, October 18, 2011

Ecological signals are complex – not simple sine tones – and not always periodic.

– Just noticeable difference (Fechner) JND, is the minimal physical change detectable by a human.

Just noticeable difference has been used as a measurement of psychological levels of stimuli.

Stevens – assessed JND agains direct subjective experience– Quite different to JND (represents difference from subject to subject baseline).

Neither approach is accurate

Pitch Perception


In Mel scale - subjective (figure 13.1) – Keyboard range adjusted to Mel scale.

Mel = unit of pitch, equal to one-thousandth of the pitch of a simple tone whose frequency is 1000 hertz and whose loudness is 40 decibels above a listener's threshold.

Pitch Perception

Closer in lower octaves, further apart in upper octaves.Mels Vs Log Freq - not linear

Mel constant – Perceived distance = log frequency scale.i.e.the Octave has the same reach = pitch doubles

On piano keyboard – not on other instruments necessarily.


Figure 13.2 graph shows how interval size changes across Mel scale.

Pitch Perception

How does this relate to the Fletcher-Munson – We are more sensitive to central frequencies so therefore our acuity is higher.

2500 Hz


Attneave and Olson (1971) also supported a logarithmic scale (see figure 13.3)

Pitch Perception

Attneave and Olson (1971) also argued - Pitch and melody are a Morphophonic Medium – relates to patterns of pitch

Pitch & time are crucial.Timbre, spatialization and loudness are secondary.

? Because they were using melodies – compositional approach pitch over time


Pitch PerceptionKubovy (1981) Dispensable versus Indispensable.

Stereo recordings use this phenomena. The signal appears to be in front of you.

Pitch is indispensable, space is dispensable

Depends on what you are listing for – – lion


Pitch PerceptionDrobisch -- tones -- helixOctaves above and below each other are associated with pitch height

Roger Shepherd, see figure 13.6

Chroma equals the distance relationship.

i.e. Imagine on 2D plane - 5 steps away but without the height represented by the helix.Chroma

Height


Pitch PerceptionDowling, Hollombe (1977) and Deutsch experimented with scrambled melodies and found that our perception of melody critically depends on high as well as Chroma.

See figure 13.11. A 4D representation equals Chroma and Height and the dimensions of the circle for the cycle of fifths.

Note – "most musically sophisticated subjects responded most to the cycle of 5ths"

? Training, cultural background, jazz or classical?


Pitch Perception

Figure 13.2, melodic space. Reference to previous paper.

Korte’s 3rd law - large steps take more time to process – melodies seem to fall apart if large steps are included. See later discussion about analysis of pitch steps in melodies.

? Vectors of change – Contour


Pitch Perception

Psychologists are not necessarily highly trained musicians. Musicians are trained to perceive "shape of phrase" and "harmonic destination".

Such training would lead to long-term perception of vectors of change as distinct from intervals. These are also memorized when learning a piece so become sub-conscious


MemoryChapter 17 – memory.

– Hippocampus and pre-frontal cortex are associated with memory– Likely to be distributed – muscle memory.

- Procedural memory - doing things– Iconic memory - images– Echoic memory - sound– Working memory - conversation - doing things now– Long term memory - life


MemoryIconic memory may be experienced as a residual image on the visual cortex.

Echoic memory - residual sound awareness - Atkinson & Shiffrin (1986)

Both deal with a sensory buffer. Immediate sensory memories are stored in a sensory buffer. Contextual constraints are associated with chunking to establish patterns to make composite elements which expands the capacity of the sensory buffer.

An example of this would be a musical chord, made up of three or more elements - perceived as one object.

It is argued that the capacity of the sensory memory is 5 to 9 elements (Miller 1956).

The Working memory (sensory buffer) is used for current functions such as conversation (Alan Badalley 1990)


Memory

Long-term memory contains the memories about life etc

- may also play a role in musical cognition in terms of references to past musical experience, and association of musical experiences with life experience.

For instance you heard that song for the first time whilst on holiday in the Caribbean.


Memory

Tulving (1985)Episodic memory – events such as birthdays holidays et ceteraSemantic memory – linked or associated – used for factsProcedural memory – tie your shoes, make coffee etc

Abstract representation – car – a class of objects, not a specific car.

You reduce - (irreducable idiostructural) – classes of objects reduce cognitive load - ie you don't have to remember ever car

– Gist of an experience – event – conversation - not the specifics.


Memory

Musical perception

Music has seven perceptual attributes – pitch, rhythm, tempo, contour, tempo, loudness.

Melody = auditory object that is maintain when attributes are altered slightly.

Melody - For instance you can alter the pitch, tempo, timbre, loudness, spatial location, and reverberation, with small variations in rhythm acceptable and with the contour change rarely acceptable.


Memory

Contour IS CriticalMemory = abstract representation of pitch invariance (Contour)

? Page 215 – "at first, the idea of contour being an important attribute of melody seems counterintuitive."

- Clearly not a train classical or jazz musician – Shown in infants and even animals.


Memory

Amusia - see Oliver Sacks.

There are interesting cases when after a stroke, the patient cannot talk, but can sing to communicate. This illustrates that different parts of the brain are engaged for speaking communication and a combination of text and melody in the production of song.


http://www.oliversacks.com/

http://www.oliversacks.com/

MemoryDaniel Levitin – long term memory includes abstract pitch representation of songs - see experiments - subjects singing a favorite rock song

– Also shows that absolute and relative information is held in the long term memory.

– Subjects were within the just noticeable difference range of 6.2 to 8% without any priming.

– This indicates relative encoding of relationships– And absolute encoding of sensory features.


http://en.wikipedia.org/wiki/Daniel_Levitin

http://en.wikipedia.org/wiki/Daniel_Levitin

Perceptual fusion + auditory perception.

John Chowning


Perceptual fusion + auditory perception.

– Periodic waveforms– quasi-periodic waveforms.

Auditory perception is extraordinarily sensitive to micro changes in quasi-periodic waveforms.

– Remember fourth tone pulse had a reverse phase and was distinct

Non-linearity – equals natural – of nature - What we used toVariations in breath, pressure etc


Perceptual fusion + auditory perception.See Figure 20.2 sung soprano voice.

Phase 1 – fundamentalPhase 2 – harmonics added – unrecognizable and voicePhase 3 – random pitch variation and vibrato added – fusing harmonics to fundamental

Commonality invariance are key to fusion – leads to stream segregation

Key to: source identification – source segregation.


Perceptual fusion + auditory perception.Experiment - singers close and far away

– Consider paper two – perception of mechanical attributes – referred to as spectral brightness – indicates more energy used in excitation of source.

– More effort for faraway signal– Perceived as more energy used in production of sound

– Relationship of timbre and intensity are critical to identification of perceptual distance.

Also consider reverberation energy– Early reflections– Secondary and main signal.

Coloration from room is clearly stronger when signal source is more distant.


Perceptual fusion + auditory perception.Loudness

Loudness constancy - Like visual constancy - we can calculate the size of an object at differing distances

– Not like perspective in vision as loudness can change suddenly and non-linearly.


pitch perception - arizona state...

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