Perception 4 - loudness and pitch

Question 1

Perceptual definition of sound

Answer 1

Sound is the experience we have when we hear

Question 2

Physical definition of sound

Answer 2

Sound is the pressure changes in the air or other medium caused by the vibration an object

Question 3

Amplitude

Answer 3

Size of the variation in air pressure
Related to perception of loudness

Question 4

Frequency

Answer 4

Number of cycles per second
related to perception of pitch

Question 5

Outer ear components

Answer 5

Pinnae
Auditory canal
Tympanic membrane

Question 6

Pinnae

Answer 6

Visible external parts of ear
Capture sound waves and funnel into auditory canal

Question 7

Auditory canal

Answer 7

~3cm tube-like structure
Protects middle ear

Question 8

Tympanic membrane

Answer 8

Cone shaped
Sound waves induce a difference in pressure either side of tympanic membrane -> vibrations
Larger amplitude -> larger vibrations

Question 9

Middle ear components

Answer 9

~2 cubic cms
Contains ossicles (3 smallest bones in human body):
-Malleus (hammer)
-Incus (anvil)
-Stapes (stirrup)
The bones amplify vibrations of the tympanic membrane and transmit them to the inner ear at the oval window

Question 10

Inner ear

Answer 10

Contains cochlea, snail-like, liquid filled organ
vibration of oval window displaces fluid -> change in pressure
Consists of 3 parallel canals

Question 11

Auditory transduction

Answer 11

Motion of the basilar membrane translated into neural signals by structures in Organ of Corti
Voltage is general when specialised hair cells in Organ of Corti are bent

Question 12

Decibel scale (dB)

Answer 12

Describes difference in amplitude
Logarithmic scale

Question 13

Rate code

Answer 13

Sound amplitude is coded in the firing rate of auditory nerve fibres
Responses increase with sound intensity

Question 14

Loudness and amplitude ….. proportional

Answer 14

Are not directly
(sounds with the same amplitude but different frequencies will differ in loudness)

Question 15

Place code

Answer 15

indicates which auditory nerve fibres respond
Sound frequencies cause a vibration in specific areas along basilar membrane
Low frequencies- near apex
High frequencies - near base

Question 16

Timing code

Answer 16

When auditory nerve fibres respond
Auditory nerve fibres are synchronised to changes of pressure (called phase locking)

Question 17

What are natural sounds made up of?

Answer 17

Fundamental r=frequency and several harmonics

Question 18

Missing fundamental illusion

Answer 18

Perceived pitch unchanged
Suggests brain infers missing fundamental from harmonics

Question 19

Pure tones

Answer 19

Sounds where pressure changes follow a sine wave and can be described by amplitude and frequency

Question 20

Complex sounds

Answer 20

made up of two or more wave forms with different frequencies