Psy100 Lecture 7
Thursday October 7, 2010
Sound Wave: amplitude determines our perception of loudness and frequency
determines our perception of pitch.
Sound: change in air pressure.
1) Sound waves go into the ear canal and vibrate the eardrum
2) The eardrum vibrates causing the ossicles (bones in the middle ear) to move
back and forth. The mechanical movement of these bones vibrates the
Lots of sound processing happens along the auditory pathway between the cochlea
and the auditory cortex. Most of this processing involves comparing the neural
signals from the two ears to analyze low-level acoustic information.
Dorsal – “where” stream, the pathway that processes spatial information. Where is
that sound coming from?
Ventral- “what” stream, the pathway that processes identify info- what kind of
sound is that?
How does the auditory system separate different sounds from one another?
Sound segregation: we must be able to segregate or separate different sounds when
they occur simultaneously.
Grouping Principles in Audition
-Gestalt grouping principles
-Common locations grouped together as one sound
Grouping by Frequency
Each component is a tone of frequency which is an integer multiple of the
fundamental frequency. All components or “harmonics” are separated by 200 Hz.
The fundamental frequency is 200 Hz. This all represents a complex harmonic
What if you mistune the second harmonic?
Mistuning means to move it up or d own in frequency so that its frequency is no
longer at an integer multiple of the fundamental frequency. A B A Paradigm
Small frequency separation between A and B tones. Grouping into 1 stream, “Gallop”
The A and B are a continuous gap.
Large frequency separation between A and B tones. Segregating into two streams
known as “streaming”
Intermediate frequency separation between A and B tones. Bi-stable perception,
sometimes “gallop” and sometimes streaming.
Imagine you’re eating at a crowded restaurant with a friend. Your friend is telling a
juicy story, but there’s lots of background noise.
Your brain has to separate your friend’s voice from all other sounds (concurrent
sound segregation and then maintain this separation) in order for you to hear and
understand your friend’s story.
Perception of sounds relies on Gestalt grouping principles.
We must separate different sounds that occur concurrently and keep them
separated over time in order to communicate effectively.
What we learn from cats
Experience teaches our brains how to perceive reality, giving us knowledge and we
use this knowledge to guide the process of constructing perceptions.
Refers to how sense organs respond to and detect external stimulus energy and how
those responses are transmitted to the brain.
Will not be tested on structure of sensory organs
Know the process
Brains further processing of detecting signals
6 steps from sensation to perception
1) Reality occurs 2) Sensory receptors contact reality
3) Transduction: physical energy of stimulus is converted into electrical energy
4) Thalamus: sensory message switchboard operator, figures out where to send
it to next.
5) Primary sensory cortex: initial processing of information occurs; area = 17
6) Further processing in many other brain areas linked to higher level cognitive
and perceptual tasks [what and where pathways]
7) Deciding & Acting: our brain decides what to do and tells