Lecture Five: Pitch Perception

1,000 Mels is the pitch of a ___ Hz tone

1,000

Listeners with SNHL, much poorer frequency discmirntion and f0 discrimination is attributed to what 2 things?

1. Loss of frequency selectivity (disruptions to the place model) *Their auditory filter's width tends to be wider compared to NL and if that's the case, their freq discrimination is poorer because in order to have a good freq discrimination, you need to have a good freq selectivity with narrow auditory filter width but if the listeners with SNHL do not have that good of freq selectivity, they show higher JND 2. Deficits in the temporal code (possibly due to distorted phase locking) *Can be explained by temporal model because those with SNHL may have poor phase locking. If the auditory neurons are not good at phase locking, that can be the factor that results in poor pitch perception which could be explained by the temporal model

What are the two models of pitch perception?

1. Place Model 2. Temporal Model

What is pitch loosely correlated with?

1. The frequency of a pure tone 2. Fundamental frequency of a harmonic sound

Subjects can still identify melodies until how many components are removed/

8-10

For Mel and frequency, what happens after 1,000 Hz

After 1,000 Hz it grows rapidly

When does Weber's law somewhat work?

Approx. 200 - 2,000 Hz weber's law somewhat works in terms of frequency discrimination. But anywhere below 200 Hz and above 2,000 Hz the Weber's fraction increases or decreases does NOT work but at the 200 - 2,000 Hz frequency range

Why does delta f increase?

At higher frequencies ( 3 - 5 kHz), the phase locking does not work well meaning you have a poorer frequency discrimination which is why delta f increases as you increase the frequency of sound

Is pitch perception straightforward?

At times Think of a simple sound -- one frequency; so pretty straightforward. However, in word acoustics, we also have complex sounds. Complex sounds has multiple frequencies. Understanding pitch perception of complex sound is not as straightforward.

Pitch perception supports auditory scene analysis, what is that?

Auditory scene analysis, a process by which we separate (or segregate) sounds from a background

What's the place model based off of?

Based on the spectral representation *In other words, it is based on the spectral information from the acoustic sound. Ex: When you listen to 1,000 Hz it stimulates most of the basal membrane which has a CF at the 1000 Hz and once the location is stimulated we perceived it as pitch for the 1,000 Hz sound

What's the temporal model based off of?

Based on the waveform representation *In other words, indicates the speed of vibration. The temporal information can give us the perception of pitch of the sound Ex: 1,000 Hz vibrates 1,000 x per second

Those who support the place model tried using the pitch of the missing fundamental to support their model, Why?

Basically, when the lower end frequency of sound (fundamental freq, first, and second harmonics) are missing, yet the pitch of that missing fundamental complex sounds are similar to the one with all harmonics still. So what they're trying to say is even though the fundamental frequencies are missing, the pitch is still in-tact meaning that the complex sounds of pitch perception are stronger related to the temporal model compared to the spectral model

Why does frequency selectivity get worse as you increase the frequency?

Because the auditory filter shape gets wider and wider at the high frequency ends that can be explained by the place model.

The FDL improves with stimulus level, where do the biggest effects occur?

Biggest effects occurred between low and mid stimulus levels -- there is different Trent at low versus high frequencies

How can we explain the temporal model of pitch perception physiologically?

By using the temporal code model

For pure tones, we measure the just noticeable frequency different, this is also called what?

Called the frequency difference limen (FDL)

Excitation patterns are used to describe which model?

Excitation patterns are used to describe place model

What's the relationship for tones above 1,000 Hz?

For the tones above 1,000 Hz there is no linear growth in Mel as frequency increases

What's the relationship for tones below 1,000 Hz for Mel and frequency?

For the tones below 1,000 Hz, there is a linear relationship between Mel and frequency

Frequency of a pure tone is coded in _____

Frequency of a pure tone is coded in the period of the waveform

Frequency of a pure tone is coded in the period of the waveform and can be represented in the ____

Frequency of a pure tone is coded in the period of the waveform and can be represented in the spectrum

What two things give us pitch perception?

Fundamental frequency and the lower harmonics give us the pitch perception

What is a complex sound?

Harmonic template models which analyzes spacing of peaks on basilar membrane representation corresponding to the harmonics. The space between peaks are determined by F0 which is the CUE for pitch of the complex sound

Explain this photo:

How the place model can be explained in physiological aspect. Maximum placement in the BM which is usually triggered by CF and that provides pitch perception for pure tones

THE FDL improves with what?

Improves with stimulus level

Pitch increases with _____

Increasing frequency

If the lower harmonics and fundamental frequency was removed, and pitch was not affected how could this phenomenon be explained?

It can be explained by the two models: place and temporal model

The FDL increases with increasing frequency, how is this consistent with the place model?

It is consistent with the place model -- frequency selectivity worsens with frequency

In low frequencies, individual auditory filters pass resolved components, the output looks like what?

It looks like a sine wave

Consistent with the place model, what does it mean by delta f increase in terms of frequency discrimination?

It means that as you increase a frequency of the stimulus, you need more differences between the two sounds in order for us to be able to discriminate between the two sounds. Discrimination gets worse as you increase the frequency (consistent with the place model).

What is resolved components in terms of spectral model?

It relates to the frequency selectivity of the auditory system and the width of the auditory filter. It is getting wider and wider at the basal end meaning that the higher frequency/higher harmonics of the complex sound are not resolved by the auditory nerves unlike the lower harmonics which really have its own auditory filter

Will removing the lower harmonics affect the pitch?

It would affect the pitch because based on the spectral model, where in the location of the cochlea was stimulated most gives us the pitch perception but if the fundamental frequency and those lower harmonics would affect the pitch however in some studies even if the fundamental frequency and lower harmonics are removed, the pitch hardly changed.

What has the highest pitch strength?

Low frequency pure tones

What's the unit of pitch called

Mel

When is diplacusis found?

Most common in asymmetric HL, but can also be present in bilateral losses

Pitch is an important aspect to what two things?

Music and speech perception

Does removing the component of a naturally occurring harmonic affect it?

No, it does not change the pitch of the stimulus

Does the period of a harmonic complex change when harmonics are removed?

No, the period of a harmonic complex does not change when harmonics are removed

What has very low pitch strength

Noises and high-frequency pure tones

How would the relationship between frequency and Mel be described?

Not straight forward

Pure tone has how many frequencies?

One frequency

How is frequency discrimination conducted for pure tones?

Participant beards interval 1 (low freq) and interval 2 (high freq) then asked which interval has the higher pitch or if they can hear the difference between the two sounds

In high frequencies, what does the auditory filter pass?

Passes unresolved components *The outputs periodic but multiple harmonics passed

What is pitch?

Perceptual attribute of sounds that allows them to make a melody and to be perceived on a scale from "low" and "high"

How do we perceive complex sounds?

Periodic, complex sounds have a harmonic relations among the harmonics within the complex sound. So, we perceive complex sounds by relying on the lower harmonics (which has the most energy)

The FDL increases with increasing frequency, how is this consistent with the temporal model?

Phase locking decreases with increasing frequency

What should be noted about this picture?

Phase locking. Auditory neurons have a phase locking which they fire at. What is phase locking? However, it should be noted that if you look at the individual fibers, they don't fire at every peak -- each fiber fires at the peak of some sine waves. It's skipping some time period but if you add all the firing fibers the same of it will look like it fires at every peak (physiologically).

Spectral and temporal information can provide ____

Pitch perception

The space between the two harmonics triggers what?

Pitch perception

Is this an example of the place model or temporal model? "When you listen to 1,000 Hz it stimulates most of the basal membrane which has a CF at the 1000 Hz and once the location is stimulated we perceived it as pitch for the 1,000 Hz sound"

Place model

Spacing between components (spectral code) support which model: the temporal model or place model?

Place model

Those who are in support of ___ model say even with the lower harmonics and fundamental frequency being removed, but the space between the components (harmonics) are in-tact and exist which is why pitch does not change much

Place model

What model does this photo represent?

Place model

What is a simple sound?

Place with the highest vibration codes for the pitch

Does the place or the temporal code account for the pitch of the missing fundamental?

Recall removing harmonic components does not remove the period of the stimulus thus a temporal model could explain the pitch of the missing fundamental *Basically, the complex sound repeats based on the rate of fundamental frequency. Even if the harmonics are gone, the periodicity is still in-tact and our brain can detect the period of the fundamental frequency, so this temporal model explains really well about the pitch of a fundamental

What HL can sometimes see diplacusis?

SNHL

Is this an example of the place model or temporal model? 1,000 Hz vibrates 1,000 x per second" "indicates the speed of vibration and that can give us information of the perception of pitch of the sound"

Temporal model

Period of stimulus (temporal code) support which model: the temporal or place model?

Temporal model

Those who are in support of __ model say when the fundamental frequency and/or lower harmonics are removed, when you gradually move the lower end harmonics the periods are the same and does not change *Periods in this situation refer to the time between the 2 spikes, the only thing that is changed is the amplitude. When you remove the components that has acoustic energy, the amplitude will be reduced. Because the period is still in-tact, the pitch perception will be similar to those who have all the harmonics.

Temporal model

What model does this photo represent?

Temporal model

The space between the two peaks are triggered by each harmonic. The space between the harmonic are the fundamental frequency, so our central nervous system does what next?

The CNS recognizes the space between the peaks and gives us the idea of fundamental frequency which is correlated to pitch perception

What is pitch strength?

The clarity of pitch

The first harmonic is ______

The first harmonic is a fundamental frequency

In complex sounds, what has the most energy?

The lower harmonics

The spacing between the components is based on the spectral information, and if we rely on that it supports what model?

The place model

What is the cute for pitch of the complex sound?

The space between peaks are determined by F0

In complex sounds, what is pitch based on?

The spectral peaks

At low SNR, we are better at understanding speech when _____

The target talker and background talker are from different speakers or speakers with different sexes

What is the temporal code based on?

The temporal code is based on pattern of neural firing of the Auditory nerve (AN) fibers which demonstrate phase locking

What does Mammalian AN fibers phase lock to pure tones with frequencies up to about 3-5 kHz?

This means that if the frequency of sound are below this frequency then the auditory system can rely on the temporal code but if it's higher than 3-5 kHz the temporal code will NOT work because neuron fibers do not generate the action potential at the faster rate. For higher frequencies, the temporal model will not work 100% of the time

What's diplacusis?

Tones with same frequency perceived at different pitches across the eats

2,000 Mels is _____

Twice the pitch of the 1000 Hz tone

When we talk about the discrimination function, we talk about ____ law

Weber's

Similar to loudness, how can we do the magnitude of pitch?

With the use of magnitude estimation

Can pitch be affected by intensity of the sound?

Yes

Is voicing information helpful in understanding speech?

Yes, esp in poorer listening conditions

Fundamental frequency is the base of the period of ______

complex sounds. Although it has multiple frequencies and vibrates based on the different harmonic components but overall is based off of the fundamental frequency

Based on Weber's law, the ratio between the delta f and f should be ___

consistent according to weber's law but does not work 100%