auditory objects in a complex acoustic environment rachele malavasi, phd institute for coastal...
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Auditory Objects In A Complex Acoustic Environment
Rachele Malavasi, PhD
Institute for Coastal Marine Environment (National Research
Council)
Oristano section, Italy
Funded by CNR ISEInstitute for Ecosistem Studies
National Research Council
the case of bird choruses
In collaboration with:Department of Human Sciences, Environment and Nature (DiSUAN)University of Urbino
ASA: suite of auditory processes invoked to explain how humans and other animals
organize the perception of complex acoustic environments into different
sources/relevant events (Bregman 1990, Hulse et al. 1997)
Auditory scene analysis in a glance
In many animal species, similar to humans: starlings (MacDougall-Shackleton et al.
1998; Bee & Klump 2004, 2005) and other birds; frogs (Gerhardt & Huber 2002);
goldfish (Fay 1998, 2000); macaques (Izumi 2001); bats (Schul & Sheridan, 2006)
Auditory objects: perceptually coherent representations of sounds, that build-up over
time / Streams: a perceptually-bound collection of sounds that together constitute an
event (Bregman 1990)
Streaming: separation of incoming auditory information into behaviorally relevant
groups, or streams. Under most natural conditions this process equates to the
separation of streams based on originating source (Knudsen 2010).
Perception of coordinated vocalizations
Brumm & Slater 2007
Malavasi & Farina 2012
Synchronized conspecific choruses of tropical
songbirds:- 3 individuals (Seddon 2002)- 4 or 5 individuals (Mann et al. 2006).
Perception of objects or combinations of objects (Griffiths and
Warren 2004) → ECONOMIC
1 set of coordinated vocalizations (choral unit) = 1 perceptual group
with different sources
Cusack et al. 2004
Perceptual units in coordinated choruses
Malavasi & Farina 2012
1 “choral unit” = 1 perceptual group
Evolution selected individuals that are more skilled at learning heterospecific songs (Malavasi & Farina 2012)
Why coordinated choruses
Interspecific coordinated choruses: provide public information (quality) and location cues (presence) influence of
communicative processes on the composition of the community (Goodale et al. 2010; Malavasi et al. 2013)
Participants preserve a shared neighbourhood of mutually supportive individuals (see Malavasi and Farina 2013), due to which they may hold
longer their territory Dear Enemy Model (Fisher 1954, Temeles 1994)
Getty 1987
Like with duets between mates, coordinated choruses seem to connect the structure
of the signal to its function (in duets, Brumm & Slater 2007)
Experience of each other’s songs, investment of time, energy (Malavasi & Farina 2012)
Malavasi et al. 2013
Channelling theory of stream segregation Tonotopic organization of auditory stream: attivation of groups
of close neurons determines the perception of tokens in one
stream (a, c) (Beauvois & Meddis, 1991, 1996; Hartmann and
Johnson, 1991; McCabe & Denham, 1997)
If the evoked neural responses are temporally coherent,
a single stream is perceived (b) (Elhihali et al. 2009)
Coherence average measure (d-f)
Bee & Mycheil 2008Shamma et al. 2011
The perceptual organization of a scene evolves over time
Temporal coherence
Temporal-coherence analysis
stage computes correlations
among the outputs of the different
feature-selective neurons
(Shamma et al. 2011)
Shamma et al. 2011
Coherence is an average measure
selection of a proper window for
temporal-coherence analysis
Perceptual grouping vs selective attention
Winkler et al. 2009, modified
Introduction of TOP-DOWN PROCESSES
(attention, memory, learning)
depend on the listener’s
experience and expectations
Selective attention: requires knowledge of the characteristics of the target of interest
(Cusack et al. 2004)
Selective attention is under conscious control of the listener’s; dependent on the
listener’s experience in selecting the same auditory pattern (Cusack et al. 2004)
Large windows…how much?
Perception is about building testable hypothesis
of the reality, based on prior knowledge and
current sensory input (Gregory 1980)
Selective attention Selective attention emergence of relevant patterns
Auditory inputs Objective information
Top-down processes
(memory, voluntary bias, learning)
Individual history
Context effect
Ecological niche
Subjective information
(individually meaningful patterns)
Streams are formed automatically or pre-attentively
Selective attention mediates between current reality, cognitive processes and the auditory input
Bottom-up processes
(neural responses, feature analysis, temporal coherence analysis)
SELECTIVE
ATTENTION
Attention + perceptual grouping → ECONOMIC strategy for ASA
PERCEPTUAL
GROUPING
Perception of coordinated vocalizations Coordinated vocalizations:
1. analysis of feature stimulus-driven
Winkler et al. 2009
Perceptual grouping of coordinated vocalizations is mediated by attention
Perceptual grouping of coordinated vocalizations is economic
2. selective attention stored knowledge and present reality
3. perceptual grouping within coherent temporal windows (regularities)
Songscope 2.4
THANKS FOR YOUR ATTENTION
6/24/13