Lecture 3 Part 1 (09-02-25)

Fundamental frequency and spectrogram

Per second gives us our fundamental frequency; shown as the lowest line on the spectrogram.
Spectrogram pronunciation note: spectrogram (sp e c t o g r a m) versus the often-mispronounced spectrogram. The transcript explicitly mentions the correct term.
Frequency axis on the spectrogram (left side) contains numbers such as:
- One important left-hand value around ~(1000\text{ Hz}) for the first major marker.
- Another value around ~(200\text{ Hz}) for a lower marker.
Hertz (Hz) is the measurement of cycles per second.
Quick takeaway: the fundamental frequency is the base rate at which the vocal system vibrates; higher harmonics build on that base.

Loudness and amplitude

Loudness is related to amplitude: greater amplitude means a louder perceived sound.
Amplitude corresponds to the size of the pressure wave: larger fluctuations between high and low pressure create louder sounds.
Real-world intuition: extremely loud events (e.g., explosions) generate powerful pressure waves capable of significant physical effects.
Practical note: amplitude is a property of the sound source and its medium, and it interacts with distance and recording conditions to determine perceived loudness.

The vocal tract as a resonating cavity

The vocal tract acts as a resonator; it shapes sounds produced by the vocal folds.
Timbre (tone color) = the spectral shape that distinguishes sounds with the same pitch and loudness; timbre is a property of the resonator and the source interaction.
Parts of the pharynx involved:
- Nasopharynx: the upper portion near the nose; part of the resonating space.
- Oropharynx: the portion behind the mouth.
- Laryngopharynx: the portion closer to the larynx/esophagus.
The pharynx is a single tube extending from the skull base to the esophagus; different sections are named for location rather than separate organs.
Why the nasopharynx is named so: it sits near the nasal cavity, i.e., part of the resonating space at the nose level.
Clinically relevant point: ENT surgeons reference specific pharyngeal regions (e.g., nasopharynx vs. laryngopharynx) to localize lesions and guide diagnoses and treatments.
The teacher advises ignoring the textbook’s section on loudness and registers due to inaccuracies; do not rely on that section for exam content.

The power-source-filter model of voice

Model components:
- Power: the breath energy supplied by the lungs.
- Source: the vibrating vocal folds in the larynx.
- Filter: the vocal tract (nasopharynx, oropharynx, laryngopharynx, and the mouth).
Overall idea: speech/voice are generated by a source of vibration (the vocal folds) that is shaped by a resonant filter (the vocal tract) and energized by the power from the lungs.

Vocal fold vibration and pitch control

The vocal folds can vibrate roughly from ~(70\text{ Hz}) up to well over ~(1000\text{ Hz}).
Relationship between frequency and pitch: for every doubling in cycles per second, pitch increases by one octave.
- Formula: $f2 = 2 f1 \quad\Rightarrow\quad \text{pitch up by 1 octave}$
How to raise pitch: elongate the vocal folds, which increases tension and reduces effective mass per vibratory cycle. This can involve:
- Lengthening (elongation) of the folds.
- Reducing mass (making the vibrating portion thinner).
- Increasing tension (tautness) of the folds.
The interplay: longer length typically yields greater tension, which often reduces the effective mass participating in each cycle.
Practical takeaway: pitch control in voice is primarily achieved by adjusting length, mass, and tension of the vocal folds.

From vocal fold vibration to heard voice: resonance and filtering

The initial sound from the vocal folds is a buzzy, glottal vibration; it is then shaped by resonance in the vocal tract.
Resonance concept:
- Resonance occurs when one vibrating system is driven by another vibration at a compatible frequency, increasing the amplitude of vibration.
- Swing analogy: pushing a swing in synchrony with its motion increases the swing’s amplitude due to resonance.
In voice: the vocal tract’s resonant properties reinforce certain frequencies (formants) and shape timbre, turning a glottal buzz into recognizable speech sounds.

Historical notes on voice registers and interpretation

The lecturer contrasts two concepts:
- Chest voice: thicker vocal fold mass, typically lower pitches, associated with “full” voice and greater vocal fold mass engagement.
- Head voice / falsetto: thinner vocal fold mass, upper-range voice. The lecturer distinguishes head voice from falsetto, arguing they are not the same even though some books treat them as a single register.
The reasoning centers on air flow and how much air passes through the vocal folds:
- More air flow can accompany a thinner vocal fold vibration, affecting perceived quality and terminology used by singers.

Qualities of voice as air flow and mass conditions change

The air flow and the mass/tension of the vocal folds determine voice quality in three broad directions:
- Breathy vs non-breathy: more air flow can produce a breathier quality; tighter closure often reduces air leakage.
- Thick vs thin mass conditions: thicker, more closed folds produce a stronger, more closed voice; thinner folds can produce lighter, brighter tones.
- Closure: reduced closure (more open) generally yields breathier or rougher sounds, while full closure yields a more blocked, pressurized voice.
Demonstrations described in the transcript (conceptual experiments):
- “Creek” (creaky voice): vocal folds vibrate erratically, are shortened, thick, and not repeating a clean vibratory cycle; sounds like noise.
- Thick, non-breathy voice (pressed): complete closure for about 50% of the cycle; loud but relatively air-blocked.
- Breathy thick voice: still relatively thick folds but with noticeable air leakage.
- Thin, upper-edge vibration (head voice / falsetto): vibrating along the upper edge with less mass participation and more air flow; may feel like a higher, lighter voice.
The transcript includes a live attempt to demonstrate these qualities, culminating in a question about whether the speaker is using a lot of air for the head-voice-like sound.

Summary: connections to fundamentals and real-world relevance

Core concepts connect to foundational acoustics: frequency, amplitude, resonance, and spectral shaping by a filter.
Real-world relevance:
- Speech intelligibility and voice quality depend on how the vocal tract filters the glottal source.
- Clinical relevance for ENT: knowing which part of the pharynx is involved helps in diagnosing pathology and planning treatment.
- Practical singing and voice training implications: understanding how length, mass, and tension of the vocal folds influence pitch and timbre; recognizing different voice qualities and their physical bases (creaky, pressed, breathy, head voice/falsetto).

Quick reference formulas and key definitions

Hertz (Hz): cycles per second; units of frequency.
Fundamental frequency: the base vibratory rate of the voice source.
Octave relationship: if $f2 = 2 f1$ , then the pitch increases by one octave.
Vocal fold vibratory range: roughly from $f \approx 70\,\text{Hz}$ to f > 1000\,\text{Hz} depending on gender, age, training, and health.
Mass–length–tension relationships:
- Longer folds + higher tension generally yield higher frequency.
- Mass per cycle decreases with mass/thinning, influencing timbre and ease of vibration.
Filter: the vocal tract (nasopharynx, oropharynx, laryngopharynx, and mouth) acts as a resonator; its shape determines formant frequencies and timbre.

Key takeaways for exam prep

Be able to define and identify the three components of the power-source-filter model and give real-world examples.
Understand how pitch relates to vocal fold length, mass, and tension, and be able to explain the octave relation with the formula $f2 = 2 f1$ .
Describe the role of the nasal/oral/laryngopharyngeal regions in shaping timbre and resonance.
Recognize the difference between chest voice and head voice/falsetto as discussed by the instructor, including the role of air flow.
Describe the different vowel- and voice-quality experiments (creaky, pressed/thick, breathy, and head-voice-like thin) and how these relate to vocal fold closure and vibratory patterns.
Connect the lecture content to clinical context (ENT localization of lesions) and to broader acoustics principles (spectrogram interpretation, amplitude vs. perceived loudness).