Auditory Perception Flashcards
Sound as Information (Spatial location)
- tells directions of events
- can tell distance to source
- can allow us to monitor surroundings without orienting
- vision does not allow this (can’t see something that has fallen behind us)
The Physical Stimulus for Sound
- Physically, sound -is the compression and spreading apart of air molecules.
- the compression and rarefaction (spreading) is caused by any movement or vibrational event in a medium such as water or air
- the disturbance in the medium spreads as a wave outward from the disturbance
- the wave propagates
sounds as info about substance
sound differences between materials (wood vs metal, etc)
The Mathematical Description of Sound - amplitude, frequency, and phase
- sound can be described as combinations of simple sinusoidal waves
- comes from Fourier
- decomposition is unique
- all components will have frequencies that are integer multiples of the lowest one
Basic Unit: the Sine Wave
- defined by frequency (amount of cycles per unit of time) and amplitude (height of each wave)
- phase: where you are in the cycle of the wave (starting at different times)
simple vs complex waves
- not many vibrations in the world are so pure so sine waves are very rare
- most sounds are complex -> combination of sine waves
Basic Structure of the Mammalian Auditory System
- ossicles
- inner ear
- cochlea
- inner hair cells
- outer hair cells
- sound waves to neural activity (final step)
Ossicles
- malleus, incus, stapes
- provides amplification which allows us to hear faint sounds
Inner ear
- made up of a collection of fluid filled chambers
- fine changes in sound pressure are translated into neural signals
- function is analogous to retina
cochlea
- spiral structure of inner ear containing organ of corti
- filled with watery fluids in three parallel canals
inner hair cells
- convey almost all information about sound waves to brain
outer hair cells
- convey info from brain
- involved in elaborate feedback system
sound waves to neural activity (final step)
- firing of auditory nerve fibers into patterns of neural activity
complex sounds
harmonics
- - lowest frequency of harmonic spectrum = fundamental frequency
- auditory system is acutely sensitive to relationships between harmonics
Sound Source Segregation
- spatial separation between sounds
- separation on basis of sound’s spectral or temporal qualities
- auditory stream segregation
Continuity and Restoration Effects
brain filling in a sound for continuity
- principle of good continuity
Timbre
Psychological sensation by which a listener can judge that two sounds that have the same loudness and pitch are dissimilar; conveyed by harmonics
cocktail party problem
- multiple sounds all overlap
- waveforms get summed into one waveform at eardrum
auditory stream segregation
perceptual organization of a complex acoustic signal into separate auditory events for which each stream is heard as a separate event
sound grouping
frequency
- continuity (following the same melody)
- timbre (telling the difference from a piano and a violin in a song)
- group by onset (common fate)
