Chapter 6- Pitch Perception Flashcards
What is pitch?
Subjective attribute of sound (like loudness).
- Varies with intensity, frequency, duration, spectrum, etc.
Pitch matches usually expressed in Hz
How is pitch measured?
Matching or scaling psychophysical methods
What is pitch height and chroma?
Height: related to actual frequency
Chroma: what note on scale
Limited to 5 kHz due to phase locking of auditory system
What is timbre?
Subjective attribute that differentiates 2 or more sounds with same: pitch, loudness, duration
Harmonics and spectral envelope varies the 2 pitches
What is the Place Theory of pitch?
Different frequencies, excite different places on BM, thus different neurons excited in neural pathway
- Or excitation pattern on BM matters
A change in frequency can be detected whenever the excitation level changes by more than a certain threshold value
What is the Temporal Theory of pitch?
Associated with neural firing pattern
- Time between spikes matters
How does Weber’s Law apply to frequency discrimination?
Plot ∆F/F as a function of F for average person
• Constant at intermediate frequencies: values near 0.002 (@40 dB SL)
Weber’s Law fails at extreme (high and low) frequency values
At low/high frequencies pitch discrimination gets worse.
Pitch discrimination is best between 600-2000 Hz
What does FMDL stand for?
Frequency modulation detection limen
What does DLF stand for?
Difference Limen for frequency
What are the predictions of the place model? What do actual data show?
Model predicts
- FDLs should vary with frequency (like ERBn)
Data show
- FDLs vary more with frequency than ERBn
- Effect of level roving small, except at high frequencies
Can the pitch theory explain the perception of complex tones?
Place theory does not explain this well.
There is not one place of maximum excitation.
What is the pitch of the missing fundamental?
An artificial stimulus was generated with the fundamental frequency missing.
Auditory system can perceive pitch of complex tone even though fundamental frequency wasn’t there.
Why can’t the place theory explain the pitch of the missing fundamental?
Place theory says that for complex tones, the energy at the fundamental frequency drives the perception of the pitch.
What matters most is the frequency between the harmonics rather than the frequency of the lowest harmonics
Periodicity/timing between peaks and waveform affects the perception
How can the template model explain virtual/residue pitch?
Brain says that the complex tone doesn’t make sense; it comes up with a template that is close to what it thinks it perceives.
Brain assumes that all tones are harmonically related.
Using this model, the brain is trying to determine the fundamental frequency of all of the components.
What are resolved harmonics?
1 harmonic is contained within a single filter
What are unresolved harmonics?
More than 1 harmonic is contained in a single filter
How can you calculate expected perceived pitch with the template model?
Pitch= ( f_n/n+ f_(n+1)/(n+1)+⋯)/N
What is some evidence against the place model?
Moore and Glasberg (1989): DLFs measured with level randomizations were smaller than predicted by the place model from 0.5-4 kHz
Moore (1972, 1973): For tone pulses presented at shorter durations, subjects did better than predicted for all frequencies up to 5 kHz
Sek and Moore (1995): FMDLs do conform fairly well to the model, but DLFs vary more with frequency than predicted by place model
Henning (1966): DLFs at high frequencies increased with level variation, but low frequencies did not. Consistent with place model for high frequencies, but not low frequencies.
Oxenham et al. (2011): Subjects can discriminate pitch well, even if missing fundamental is missing.
What is some evidence against the temporal model?
Oxenham et al. (2011): Demonstrated phase locking to stimulus above 6 kHz, which is above accepted limit to phase locking in auditory neural structures. Not explained by temporal theory.
What is virtual pitch?
Artificial complex stimulus was generated with the fundamental frequency missing. Yet the missing fundamental is still perceived (residue pitch)
The frequency between the harmonics matters more for pitch perception than the fundamental frequency.
How did Oxenham et al. 2011 assess the pitch of very high harmonics?
Assessed the limits of pitch, resolved partials, and melody perception in humans using pure and complex tones.
Results:
Phase locking of the stimulus above 6 kHz, which is above the accepted limit for phase locking in auditory neural structures (~5 kHz).
• Complex tones w/ fundamental frequencies below 2 kHz, and harmonics above 6 kHz, can elicit robust pitch perception
• A listener’s auditory experience and exposure to harmonic sounds is a possible explanation
