Auditory Perception

Question 1

Sound as Information (Spatial location)

Answer 1

• 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)

Question 2

The Physical Stimulus for Sound

Answer 2

• 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

Question 3

sounds as info about substance

Answer 3

sound differences between materials (wood vs metal, etc)

Question 4

The Mathematical Description of Sound - amplitude, frequency, and phase

Answer 4

• 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

Question 5

Basic Unit: the Sine Wave

Answer 5

• 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)

Question 6

simple vs complex waves

Answer 6

• not many vibrations in the world are so pure so sine waves are very rare
• most sounds are complex -> combination of sine waves

Question 7

Basic Structure of the Mammalian Auditory System

Answer 7

• ossicles
• inner ear
• cochlea
• inner hair cells
• outer hair cells
• sound waves to neural activity (final step)

Question 8

Ossicles

Answer 8

• malleus, incus, stapes

- provides amplification which allows us to hear faint sounds

Question 9

Inner ear

Answer 9

• made up of a collection of fluid filled chambers
• fine changes in sound pressure are translated into neural signals
• function is analogous to retina

Question 10

cochlea

Answer 10

• spiral structure of inner ear containing organ of corti

- filled with watery fluids in three parallel canals

Question 11

inner hair cells

Answer 11

• convey almost all information about sound waves to brain

Question 12

outer hair cells

Answer 12

• convey info from brain

- involved in elaborate feedback system

Question 13

sound waves to neural activity (final step)

Answer 13

• firing of auditory nerve fibers into patterns of neural activity

Question 14

complex sounds

Answer 14

harmonics
- - lowest frequency of harmonic spectrum = fundamental frequency

• auditory system is acutely sensitive to relationships between harmonics

Question 15

Sound Source Segregation

Answer 15

• spatial separation between sounds
• separation on basis of sound’s spectral or temporal qualities
• auditory stream segregation

Question 16

Continuity and Restoration Effects

Answer 16

brain filling in a sound for continuity

- principle of good continuity

Question 17

Timbre

Answer 17

Psychological sensation by which a listener can judge that two sounds that have the same loudness and pitch are dissimilar; conveyed by harmonics

Question 18

cocktail party problem

Answer 18

• multiple sounds all overlap

- waveforms get summed into one waveform at eardrum

Question 19

auditory stream segregation

Answer 19

perceptual organization of a complex acoustic signal into separate auditory events for which each stream is heard as a separate event

Question 20

sound grouping

Answer 20

frequency

• continuity (following the same melody)
• timbre (telling the difference from a piano and a violin in a song)
• group by onset (common fate)