Vocal cords are two folds of muscular and ligamentous tissue located in the larynx, at the entrance to the trachea. By vibrating as exhaled air passes through, they produce a sound that is then modulated by the vocal tract to form speech and singing.
Discover FizziQ
How to measure it in class
With the FizziQ app, it is possible to analyze the characteristics of the voice.
Steps:
- Open FizziQ and select the “Frequency meter” instrument
- Pronounce a sustained vowel (aaaa) and measure the fundamental frequency
- Compare the frequencies of different voices (man, woman, child)
- Use the spectrogram to visualize the harmonics of the voice
- Observe the characteristic formants of each vowel
- Compare speaking voice and singing voice
Scientific activities on this topic
- Vowel analysis: https://www.fizziq.org/en/activities/vowels/
- Study of voice pitch according to age and sex
- Link between anatomy and vocal acoustics
Learn more
Anatomy of the vocal cords:
Vocal cords measure approximately 15-20 mm in women and 20-25 mm in men. They are controlled by several muscles that adjust their tension, position, and thickness.
Phonation mechanism:
- The vocal cords come together (adduction)
- Exhaled air creates subglottic pressure
- This pressure pushes the vocal cords apart
- The airflow causes pressure to drop (Bernoulli effect)
- The vocal cords close again
- The cycle repeats at high frequency
Vocal frequencies:
| Voice type | Fundamental frequency |
|---|---|
| Bass (male) | 80 - 165 Hz |
| Tenor (male) | 130 - 260 Hz |
| Alto (female) | 175 - 350 Hz |
| Soprano (female) | 260 - 520 Hz |
| Child | 250 - 400 Hz |
Male/female differences:
Male vocal cords are longer and thicker, resulting in a lower fundamental frequency. At puberty, the growth of the larynx (Adam’s apple) causes the male voice to drop by about one octave.
Formula
The vibration frequency of the vocal cords can be approximated by:
f = (1/2L) x sqrt(T/rho)
where:
- f: fundamental frequency (Hz)
- L: length of the vocal cords (m)
- T: tension (N/m^2)
- rho: linear density of the tissue (kg/m)
In practice, tension control is the main mechanism for changing pitch.
Application examples
- The average frequency of an adult male voice is around 120 Hz
- An opera singer can vary their voice over more than 2 octaves
- Children’s voices have similar frequencies regardless of sex
- Hoarseness corresponds to irregular vibration of the vocal cords
FAQ
Q: Why are vocal cords called “cords” when they don’t look like instrument strings? A: The term comes from their elongated shape. They are also called “vocal folds,” which better describes their actual anatomy.
Q: How do we sing different notes? A: By modifying the tension of the vocal cords through the laryngeal muscles. The higher the tension, the higher the vibration frequency, and the higher the pitch.
Q: Can you see the formants of your voice with FizziQ? A: Yes, the spectrogram shows formants as horizontal bands of reinforced energy. They characterize vowels and individual vocal timbre.
Q: Do vocal cords wear out? A: Yes, excessive or incorrect use can cause nodules or lesions. Singers and teachers must learn proper voice placement.
Related concepts
Formants - Fundamental frequency - Timbre - Pitch - Spectrogram - Phonation - Speech acoustics