Source Segregation Chris Darwin Experimental Psychology University of Sussex Nee
Itow, Joanne, Managing Partner;Research Consultant has reference to this Academic Journal, PHwiki organized this Journal Source Segregation Chris Darwin Experimental Psychology University of Sussex Need as long as sound segregation Ears receive mixture of sounds We hear each sound source as having its own appropriate timbre, pitch, location Stored in as long as mation about sounds (eg acoustic/phonetic relations) probably concerns a single source Need to make single source properties (eg silence) explicit
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Making properties explicit Single-source properties not explicit in input signal eg silence (Darwin & Bethel-Fox, JEP:HPP 1977) NB experience of yodelling may alter your susceptibility to this effect Mechanisms of segregation Primitive grouping mechanisms based on general heuristics such as harmonicity in addition to onset-time – bottom-up / pure audition Schema-based mechanisms based on specific knowledge (general speech constraints) – top-down. Segregation of simple musical sounds Successive segregation Different frequency (or pitch) Different spatial position Different timbre Simultaneous segregation Different onset-time Irregular spacing in frequency Location (rather unreliable) Uncorrelated FM not used
Successive grouping by frequency Track 8 Track 7 Bug in addition to an xylophone music: Ssematimba ne Kikwabanga Not peripheral channelling Streaming occurs as long as sounds with same auditory excitation pattern, but different periodicities Vliegen, J. in addition to Oxenham, A. J. (1999). “Sequential stream segregation in the absence of spectral cues,” J. Acoust. Soc. Am. 105, 339-46. with Huggins pitch sounds that are only defined binaurally Carlyon & Akeroyd Huggins pitch ø
Successive grouping by frequency Track 2 Successive grouping by spatial separation Track 41 Sach & Bailey – rhythm unmasking by ITD or spatial position ITD sufficient but, sequential segregation by spatial position rather than by ITD alone. Target ITD=0, ILD = 0 Target ITD=0, ILD = +4 dB Masker
Build-up of segregation Horse Morse -LHL-LHL-LHL- -> -H–H–H- -L-L-L-L-L-L-L Segregation takes a few seconds to build up. Then between-stream temporal / rhythmic judgments are very difficult Some interesting points: Sequential streaming may require attention – rather than being a pre-attentive process. Attention necessary as long as build-up of streaming (Carlyon et al, JEP:HPP 2000) Horse Morse -LHL-LHL-LHL- -> -H–H–H- -L-L-L-L-L-L-L Horse -> Morse takes a few seconds to segregate These have to be seconds spent attending to the tone stream Does this also apply to other types of segregation
Capturing a component from a mixture by frequency proximity A-B A-BC Freq separation of AB Harmonicity & synchrony of BC Simultaneous grouping What is the timbre / pitch / location of a particular sound source Important grouping cues continuity onset time harmonicity (or regularity of frequency spacing) (Old + New) Bregmans Old + New principle Stimulus: A followed by A+B -> Percept of: A as continuous (or repeated) with B added as separate percept
Old+New Heuristic B MAMB A MAMB Percept M Grouping & vowel quality
Grouping & vowel quality (2) Onset-time: allocation is subtractive not exclusive Bregmans Old-plus-New heuristic Indicates importance of coding change. Asynchrony & vowel quality 90 ms T Onset Asynchrony T (ms) F1 boundary (Hz) 8 subjects No 500 Hz component
Mistuning & pitch Mean pitch shift (Hz) % Mistuning of 4th Harmonic 8 subjects 90 ms Onset asynchrony & pitch Onset Asynchrony T (ms) Mean pitch shift (Hz) 8 subjects ±3% mistuning 90 ms T Some interesting points: Sequential streaming may require attention – rather than being a pre-attentive process. Parametric behaviour of grouping depends on what it is as long as .
Grouping as long as Effectiveness of a parameter on grouping depends on the task. Eg 10-ms onset time allows a harmonic to be heard out 40-ms onset-time needed to remove from vowel quality >100-ms needed to remove it from pitch. Minimum onset needed as long as : Grouping not absolute in addition to independent of classification group classify
Speech music Bregman long summary Cues used by the ASA process The perceptual segregation of sounds in a sequence depends upon differences in their frequencies, pitches, timbres (spectral envelopes), center frequencies (of noise b in addition to s), amplitudes, in addition to locations, in addition to upon sudden changes of these variables. Segregation also increases as the duration of silence between sounds in the same frequency range gets longer. The perceptual fusion of simultaneous components to as long as m single perceived sounds depends on their onset in addition to offset synchrony, frequency separation, regularity of spectral spacing, binaural frequency matches, harmonic relations, parallel amplitude modulation, in addition to parallel gliding of components. [Note to physicists: All these cases of fusion can be obtained at room temperature.] Different cues as long as stream segregation compete to control the grouping, in addition to different cues have different strengths. Primitive grouping occurs even when the frequency in addition to timing of the sequence is unpredictable. An increased biasing toward stream segregation builds up with longer exposure to sounds in the same frequency region. Stream segregation is context-dependent, involving the competition of alternative organizations, Effects of ASA on perception A change in perceptual grouping can alter the perception of rhythms, melodic patterns, in addition to overlap of sounds. Patterns of sounds whose members are distributed into more than one perceptual stream are much harder to perceive than those wholly contained within a single stream. Perceptual organization can affect perceived loudness in addition to spatial location. The rules of ASA try to prevent the crossing of streams in frequency, whether the acoustic material is a sequence of discrete tones or continuously gliding tones. Known principles of ASA can predict the camouflage of melodies in addition to rhythms when interfering sounds are interspersed or mixed with a to-be-recognized sequence of sounds. The apparent continuity of sounds through masking noise depends on ASA principles. Stimuli have included frequency glides, amplitude-varying tones, in addition to narrow-b in addition to noises. A perceptual stream can alter another one by capturing some of its elements. The apparent spatial position of a sound can be altered if some of its energy becomes grouped with other sounds, Comodulation masking release (CMR) does not make the presence of the target more discriminable by simply altering the timbre of the target-masker mixture. It actually increases the subjective experience that the target is present. Sequential capturing can affect the perception of speech, specifically the integration of perceptually isolated components in speech-sound identification. The segregation of vowels increases when they have different pitches in addition to different pitch transitions. We have looked at synthetic vowels that do or do not have harmonic relations between frequency components, ASA principles help explain the construction of music, e.g., rules of voice leading. ASA principles are used intuitively by composers to control dissonance in polyphonic music. The segregation of streams of visual apparent motion works in exactly the same way as auditory stream segregation.
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