Pitch Perception

Question 1

What is pitch?

Answer 1

• Subjective attribute equivalent to frequency
• Varies with intensity, frequency, duration, spectrum, etc.
• Pitch matches usually are expressed in Hz

Question 2

What is pitch height?

Answer 2

• Related to actual frequency correspondent of pitch
• Describes perceptual “highness” or “lowness” of a pitch
• Perceptual differences between 2 notes that share the same pitch chroma
• Limited to 5 kHz (due to poor phase-locking at the AN above that frequency)

Question 3

What is chroma?

Answer 3

• What note on scale
• Describes the perceptual “differences/distances” of pitches within an octave or pitches separated by 1+ octave
• Limited to 5 kHz (due to poor phase-locking at the AN above that frequency)

Question 4

What is timbre?

Answer 4

• Subjective attribute that differentiates 2+ sounds with the same pitch, loudness, duration, etc.
• Due to spectral shape (harmonics’ effect on spectrum)

Question 5

What is a “resolved” harmonic?

Answer 5

-When 1 harmonic falls within an auditory filter

Question 6

What is an “unresolved” harmonic?

Answer 6

• When more than one harmonic falls within a single auditory filter
• Components interact when unresolved

Question 7

What is Weber’s law for frequency?

Answer 7

• Weber’s fraction: just noticeable difference (delta F) as a proportion of stimulus frequency (F) –> (delta F)/F
• Plotted as a function of F for the average person
• Constant at intermediate frequencies from 600-2000 Hz: values near .002 (@40 dB SPL)
• Weber’s law fails at extreme (high and low) frequencies

Question 8

How do you calculate if two frequencies are discriminable according to Weber’s law for frequency?

Answer 8

• Calculate (delta F)/F

- If Weber’s law is working, Weber’s fraction should be extremely low (~.002)

Question 9

How can you calculate perceived pitch with template model?

Answer 9

• Template model says that your brain knows how harmonic complexes are made (sounds come from physical resonating bodies with harmonic structures)
• Instead of perceiving GCD, the brain’s perceived pitch is relatively close to the frequency of the missing fundamental
• Perceived pitch = (Fn/n + Fn+1/n+1 +…]/N

Question 10

Describe Zwicker’s place model.

Answer 10

-A change in frequency can be detected by a change in excitation level, so frequency detection limen should be a constant fraction of its ERBn at that frequency

Question 11

What does Zwicker’s place model predict?

Answer 11

• FDLs should vary with frequency (like ERBRn which dictates the size of the excitation pattern)
• Level roving should markedly increase FDLs

Question 12

What does the data show about Zwicker’s place model?

Answer 12

• FDLs vary more with frequency with ERBn
• Effect of level roving small, except at high frequencies (may be due to transducers)

-Thus, place model has difficulty explaining data

Question 13

Describe Place Theory of pitch perception.

Answer 13

• Different frequencies excite different places on the BM, thus different neurons excited in the neural pathway
• OR excitation pattern matters

Question 14

What evidence negates Place Theory?

Answer 14

1) Pitch of the missing fundamental
2) Stretched octave
3) Perception of musical intervals <5 kHz
4) Pitch of complex tones: more than one place of maximum excitation
5) Degradation of pitch at high frequencies where phase-locking is thought to degrade
6) Remarkable ability to discriminate the frequency of pure tones: Zwicker’s model cannot explain how DLFs vary with frequency
7) Variation of pitch with level: <2 kHz pitch decreases with increased level; ~4 kHz pitch increases with increased level
8) Variation of pitch with level randomization: should greatly increase with DLFs

Question 15

Describe Temporal Theory of pitch perception.

Answer 15

-Perceived pitch is associated with neural firing pattern, specifically time between spikes

Question 16

What evidence supports Temporal Theory?

Answer 16

-Pitch of the missing fundamental

Question 17

What evidence supports Place Theory?

Answer 17

-

Question 18

What evidence negates Temporal Theory?

Answer 18

• Oxenham et al. (2011)
• Presented subjects with pure tones and harmonic complex tones to test the upper frequency limit on pitch and melody perception
• However, if the harmonic spacing is very large, the harmonics would remain resolved (residue pitch could not be restored to the temporal envelope)
• This, combined with the lack of phase-locking above 4 kHz, means that these data cannot be explained by a temporal model (could be explained by a template model?)

Question 19

What is virtual pitch?

Answer 19

• Perceived pitch, aka residue pitch
• Explains pitch of the missing fundamental
• For complex tones, energy at F0 drives the percept
• However, frequency between harmonics matters more than F0 (timing between peaks in the waveform)

Question 20

Describe the pitch of very high harmonics as is seen in Oxenham et al. (2011).

Answer 20

• Presented subjects with pure tones and harmonic complex tones to test the upper frequency limit on pitch and melody perception
• However, if the harmonic spacing is very large, the harmonics would remain resolved (residue pitch could not be restored to the temporal envelope)
• This, combined with the lack of phase-locking above 4 kHz, means that these data cannot be explained by a temporal model (could be explained by a template model?)