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Pitch Part 1 - lecture notes

lecture notes
Course

Introduction to Hearing Sciences (CSD:3113)

29 Documents
Students shared 29 documents in this course
Academic year: 2022/2023
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University of Iowa

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Pitch Perception:

  • Pitch of pure tones ◦ place theory ◦ timing theory
  • Pitch of complex tones ◦ pattern matching model- similar to place theory model ◦ temporal model ◦ duplex theory

Pitch:

  • ANSI (national standard for hearing and loudness)- "that attribute of auditory sensation in terms of which sounds may be ordered on a scale extending from low to high"may be ordered on a scale extending from low to high"
  • Plack- “The aspect of auditory sensation whose variation is associated with musical melodies”
  • Pitch- our personal sensation
  • Physical attribute of pitch = frequency

Pitch of Pure Tones:

  • Main question- what code people use to figure out what the frequency of a pure tone is?
  • Place theory- the pitch of the sound is assumed to be related to the excitation pattern it produces on the BM ◦ the pitch of a pure tone may be explained by the position of maximum excitation
  • Temporal theory- the waveform of a sound with a strong pitch is periodic ◦ the basis for the pitch performance is the timing of neural firings, which occur in response to vibrations on the basilar membrane ◦ Phase locking- nerve firings occur at particular phases of the waveform ‣ occurs for low frequency tones ‣ temporal coding cannot contribute to the perception of high frequency pure tones
  • Pitch mechanism depends on frequency- both temporal and place codes are used to perceive the pitch of low frequency tones ◦ place code is used for the pitch perception of high frequency pure tones ‣ temporal code cannot be used for the pitch perception of high frequency pure tones due to the lack of phase locking
  • For the pitch perception of pure tones, people use Place Theory code at high frequencies

Pitch of Complex Tones: fundamental and harmonics

  • Helmholtz's place theory (grandfather of hearing science)- pitch is frequency of fundamental coded by place of excitation ◦ only care about the sound closest to the apex of our cochlea ◦ problem- fundamental not necessary for pitch ‣ missing fundamental = no fundamental but we still hear the pitch at 200Hz
  • Pattern Recognition- based on the rate-place code ◦ BM activation pattern evoked by a complex tone
  • Temporal Models- based on the temporal code ◦ the phase locked response of the auditory nerve fibers
  • Beats- when two sine waves are added ◦ distortion, a ringing sound when they are of similar frequencies
  • Resolved vs Unresolved harmonics in auditory filters- ◦ resolved = harmonics different auditory filters (low frequencies)

temporal = low frequencies

‣ a different set of harmonics will create a different activity pattern across filters ◦ unresolved = harmonics fall into the same auditory filters (high frequencies) ‣ pass through the auditory filter ‣ different sets of harmonics could create the same pattern of activity across filters ‣ filters are wider at high frequencies

  • Temporal response to resolved and unresolved harmonics ◦ resolved- the neurons will be phase locked to the fine structure of each harmonic ◦ unresolved- the neurons will be phase locked to the envelop of the sound which has a periodicity of 200 Hz (fundamental frequency)
  • Pattern matching models: pitch is based on resolved harmonics ◦ harmonic template is used to determine the pitch ◦ brain estimates frequencies of resolved harmonics ‣ could be by a place mechanism and or through phase locked timing information ◦ then finds the sub-harmonic number for those frequencies ‣ 401, 602, 804 -> pitch of 200 Hz ◦ TRUE or FALSE - pattern recognition theories would predict that complex pitch perception will be good with unresolved harmonics ◦ TRUE or FALSE - Temporal theories would predict that complex pitch perception will be good with unresolved harmonics
  • Pattern recognition vs temporal theories: evidences (pattern recognition is used more because it is easier) ◦ existence region of virtual pitch ‣ can you get virtual pitch with harmonics too high to be resolved? YES ◦ dominance region ‣ which harmonics are most important to determining pitch? RESOLVED HARMONICS ◦ resolved harmonics produce stronger impressions of pitch ‣ support pattern recognition theories ◦ virtual pitch dos occur when all harmonics are unresolved ‣ temporal information is also being used
  • Two pitch mechanisms- Duplex theory ◦ duplex theory- pattern matching models could be good as the main pitch mechanism (we use both theories to understand complex tones) ‣ temporal mechanisms for unresolved harmonics ‣ pitch perception must involve neural, central processes ◦ in complex pitch, temporal code would be most important for _____
  • Components of pitch sensation ◦ Shepard's double helix- pitch height and chroma ‣ this is to account for the perceived similarity of pitches that are separated by octaves ◦ pitch height- the low/high dimension of pitch ◦ chroma- the relative position of a pitch within a given octave ◦ tones are judged to be more similar when they share chroma
  • Pitch ogranization in Western tonal music ◦ two notes are octave apart if their frequencies are in the ratio 2: ◦ in equal tempered tuning the octave is divided into 12 logarithmic steps called semitones ◦ the fundamental frequency of adjacent semitones differs by a factor of 2^1/ ◦ semitone may be subdivided into "cents" ◦ there are 100 cents in a semitone and 1200 cents in an octave ◦ NOT ON MIDTERM Review:
  • Two mechanisms for pure-tone pitch perception ◦ place coding- good for any frequencies ◦ temporal coding- good for low frequencies
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Pitch Part 1 - lecture notes

Course: Introduction to Hearing Sciences (CSD:3113)

29 Documents
Students shared 29 documents in this course

University: University of Iowa

Was this document helpful?
Pitch Perception:
Pitch of pure tones •
place theory ◦
timing theory ◦
Pitch of complex tones •
pattern matching model- similar to place theory model ◦
temporal model ◦
duplex theory ◦
Pitch:
ANSI (national standard for hearing and loudness)- "that attribute of auditory sensation in terms of which •
sounds may be ordered on a scale extending from low to high"may be ordered on a scale extending from low
to high"
Plack- “The aspect of auditory sensation whose variation is associated with musical melodies” •
Pitch- our personal sensation
•
Physical attribute of pitch = frequency
•
Pitch of Pure Tones:
Main question- what code people use to figure out what •
the frequency of a pure tone is?
Place theory- the pitch of the sound is assumed to be •
related to the excitation pattern it produces on the BM
the pitch of a pure tone may be explained by the ◦
position of maximum excitation
Temporal theory- the waveform of a sound with a strong pitch is periodic •
the basis for the pitch performance is the timing of neural firings, which occur in response to vibrations ◦
on the basilar membrane
Phase locking- nerve firings occur at particular phases of the waveform
◦
occurs for low frequency tones
‣
temporal coding cannot contribute to the perception of high frequency pure tones ‣
Pitch mechanism depends on frequency- both temporal and place codes are used to perceive the pitch of low •
frequency tones
place code is used for the pitch perception of high frequency pure tones ◦
temporal code cannot be used for the pitch perception of high frequency pure tones due to the lack ‣
of phase locking
For the pitch perception of pure tones, people use Place Theory code at high frequencies
•
Pitch of Complex Tones: fundamental and
harmonics
Helmholtz's place theory (grandfather of hearing science)- pitch is frequency •
of fundamental coded by place of excitation
only care about the sound closest to the apex of our cochlea ◦
problem- fundamental not necessary for pitch ◦
missing fundamental = no fundamental but we still hear the pitch at ‣
200Hz
Pattern Recognition- based on the rate-place code •
BM activation pattern evoked by a complex tone ◦
Temporal Models- based on the temporal code •
the phase locked response of the auditory nerve fibers ◦
Beats- when two sine waves are added •
distortion, a ringing sound when they are of similar frequencies ◦
Resolved vs Unresolved harmonics in auditory filters- •
resolved = harmonics different auditory filters (low frequencies) ◦
temporal = low frequencies

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