pitch perception

Question 1

what is pitch

Answer 1

the perceived frequency of a sound with high pitch perceived as high frequency sound and low pitch as low frequency sound

Question 2

what does pitch do for us

Answer 2

enables us to distinguish between different background sounds and between people as vocal cords of individuals differ, as well as changing the emphasis of words lead to different meanings.

Question 3

what is a period?

Answer 3

the time required for one complete cycle of a wave composed of a repeating peak and trough to pass by a point

Question 4

what are the types of sounds that can evoke pitch perceptions?

Answer 4

complex periodic tones
SAM tones
pure tones

Question 5

describe the types of sounds that can evoke pitch perceptions.

Answer 5

pure tone: is the simplest tone with pure sinusoidal oscillations comprised of a single frequency with a single harmonic that has a regular repeating pattern translating into its period.

complex periodic tones: have a regular repeating pattern that translates into its periodicity due to multiple harmonics, which are multiple integers of the fundamental frequency. Each harmonic has its own period, but the combined form is known as its periodicity.

SAM tones: this is a sinusoidally amplitude-modulated tone: In the time domain, the waveform is in a regular repeating pattern due to the modulation frequency (i.e., that can occur every 2.5 milliseconds), corresponding to its periodicity, such that the waveform can change its repetitive patterns (as its manipulated by researchers). In the frequency domain, however, the modulation frequency is not shown only the carrier frequency (the main frequency that you start with, but then you change it to the modulation frequency)
and is in between the side bands. the sidebands is the carrier frequency + / - the modulation frequency

Question 6

what is periodicity and how can that be represented for a complex periodic tone

Answer 6

repetition rate of a waveform

as complex periodic tones have multiple frequencies (multiple integers of fundamental frequency).
The periodicity will correspond to the compound waveform repeating at an interval or rate equal to the fundamental frequency

Question 7

do complex aperiodic sounds have periodicity?

Answer 7

they contain multiple frequencies but they aren’t harmonics, ie not multiple integers of the fundamental frequency so there is no repetition in the time domain of a wave

Question 8

is periodicity or period a time domain or frequency domain aspect?

Answer 8

time domain

Question 9

what are the two ways in which we decode pitch?

Answer 9

-tonotopy-place coding
location of frequency-sensitive inner hair cells along the basilar membrane of the cochlear in the inner ear, which vibrate strongly to its preferred or sensitive sound wave. these vibrations are converted to electrical impulses propagating along the AN afferents and sent to higher centres in the brain for decoding

-phase locking- temporal coding
involves the synchronised firing of the AN afferents to the regular repeating pattern of a sound wave corresponding to its peak and trough, which confers information about its precise timings

Question 10

spacial and temporal filtering in the cochlea

Answer 10

Frequency tuning along the cochlear length shows that:
Low-numbered harmonics can be easily resolved
High-numbered harmonics cannot be resolved easily as they are more broadly tuned. (it’s not specific enough to be defined.)

Question 11

could you read the pitch from the fundamental frequency?

Answer 11

You can normally read the pitch from the fundamental frequency; however, in situations where there is a missing fundamental frequency, the pitch could be read off by the spacing between harmonics corresponding to the pitch of the fundamental frequency, even though it’s missing in this case.

Question 12

tone with harmonics of 400,600,800.., what frequency will the pitch be?

Answer 12

200 Hz

Question 13

tone with harmonics of 400, 800,1200.., what frequency would the pitch be?

Answer 13

400Hz

Question 14

how could the pitch of a SAM tone be coded
temporal coding
place coding
both?

Answer 14

temporal coding
as you cant get place coding, there is no harmonic band corresponding to its pitch, so there’s only information about its periodicity

Question 15

can non-human mammals perceive pitch?
help (do we include the experiment)

Answer 15

most likely as they have tonotopic organisations in their auditory systems; hence, it allows the ability to discriminate between frequency ranges.

Question 16

what is the limit of phase locking of neurons to the periodicity of a complex periodic sound?

Answer 16

4 kilohertz

Question 17

what are interspike intervals?

Answer 17

spikes of a single neurone

Question 18

in cortex, how do we relate phase locking too

Answer 18

Normally, auditory nerve afferents are able to phase lock to high frequencies limited to 4 kilo Hz. However, neurons in the auditory cortex are only able to phase lock to frequencies up to low hundreds, which means the temporal code will need to be represented by a rate-based code rather than phase locking.

rate-based code is the firing rate of the neurons such that when their preferred periodicity is present, their firing rate will increase.

Question 19

quickly name the different ways in which pitch can be coded

Answer 19

temporal phase locking
place decoding
rate-based code