Audition (L6)

Question 1

Sound

Answer 1

• A sound is a periodic compression of air/water

- An object vibrates the air and sets up sound waves that hit the ear

Question 2

Where is the auditory cortex found?

Answer 2

• Broadmann’s area 41 and 42

- Heschi’s gyrus

Question 3

Amplitude

Answer 3

• How much air fluctuation the sound creates
• Measured in decibels (dB)
• Perceived as loudness
• Sounds above 85dB can cause hearing damage

Question 4

How is sound intensity encoded for frequencies above 200Hz?

Answer 4

Neuron firing rate

Question 5

How is sound intensity encoded for frequencies below 200Hz?

Answer 5

The number of neurons firing

Question 6

Frequency

Answer 6

• The number of air compression per second that an object creates
• Measured in Hertz (Hz)
• Perceived as pitch

Question 7

The place code

Answer 7

• Different places along the cochlea respond to different sound frequencies because of differences in stiffness/elasticity of the cochlear membrane
• Low frequency sounds move the apex, high frequency sounds move the base

Question 8

The temporal code

Answer 8

• For frequencies below 200Hz
• The basilar membrane vibrates in synchrony with a sound, causing auditory nerve axons to produce action potentials with the same frequency

Question 9

What happens in the outer ear?

Answer 9

Captures the sound and amplifies it by funnelling it into the smaller auditory canal

Question 10

What happens in the middle ear?

Answer 10

The eardrum (tympanic membrane) collects the vibrations and transmits them to the ossicles (hammer, anvil and stirrup) whose lever action transfers the vibration to the cochlea via the oval window

Question 11

What happens in the inner ear?

Answer 11

• The stirrup sends vibrations throughout the cochlea and to the organ of corti (contains four rows of hair cells embedded in the basilar membrane)
• Vibration moves the basilar membrane = bends the hair cells = opens K+ and Ca2+ channels = depolarisation = hair cells synaptically excite the cells of the auditory nerve

Question 12

Auditory pathway

Answer 12

1. Ipsilateral cochlear nuclei in the brain stem receive input from the auditory nerve
2. Signal relays to the superior olivary nucleus in the brain stem
3. Relays to the inferior colliculus of the midbrain
4. Relays to the thalamus
5. Projects to the auditory cortex

Question 13

Relative pitch

Answer 13

A musician’s ability to identify the intervals between given tones

Question 14

Absolute pitch

Answer 14

A musician’s ability to name/reproduce a musical note without external reference

Question 15

Amusia

Answer 15

• Receptive: inability to recognize familiar melodies, read musical notation, inability to detect wrong or out-of tune notes
• Expressive: the loss of ability to sing, write musical notation, play an instrument

Question 16

Conductive hearing loss

Answer 16

• Results from damage to the eardrum or ossicles in the middle ear = failure to transmit sound waves to the cochlea
• Corrected by medication, surgery, hearing aids, or by using bone conduction

Question 17

Sensorineural hearing loss

Answer 17

• Damage to the cochlea/hair cells in the inner ear
• Corrected by cochlear implants (surgically implanted electronic device which receives a sound signal via a microphone and conducts it via thin wires to directly stimulate the auditory nerve)

Question 18

Tinnutus

Answer 18

• Perception of sound in the absence of external source

- Persistent ringing caused by abnormal patterns of activity or plastic changes in the brain

Question 19

Complexity

Answer 19

• Perceived as timbre (sound quality)

- Can be simple, pure tones or a mix of frequencies

Question 20

Localising a sound

Answer 20

• Sounds waves arrive sooner and appear louder at ear closer to source
• Visual orienting moves the eyes towards a target making sound