The Vocal Mechanism, Part II
Last time we talked about the major structures used in creating the voice--the lungs (which provide airflow and power to the vocal folds for vibration), the larynx (which houses the vocal folds, muscles, and cartilages used to vary pitch), and the vocal tract which includes the structures of the throat, mouth, and sinuses that shape the quality of the vocal fold vibrations to provide us with our unique voice.
Today we will talk a bit more about the workings of the larynx and vocal tract in generating the voice.
And three paired cartilages:
These can be seen in the image below:
These cartilages work to both protect the vocal folds and help with movement to alter pitch and loudness.
Several muscles are contained both within and outside of the larynx that help move the structures and vocal folds as well. The internal muscles can be noted here:
Through these muscles the vocal folds can be brought together, pulled apart, and changed in length and shape to create a variety of different sounds.
Let's watch a video showing some movements the larynx and vocal folds can make when we produce varying pitches and speech sounds:
We can see how the vocal folds are pulled taut and thinner to create higher pitches, and brought together and made "fatter" to create lower pitches.
When pitch is measured, it is referenced in a number form in Hertz, abbreviated Hz, and is what is perceptually heard from the fundamental frequency (f₀) of the vibration (a future post).
Today we will talk a bit more about the workings of the larynx and vocal tract in generating the voice.
The Larynx and the Vocal Folds
The larynx provides housing for the vocal folds, which are the source of vibration/sound for our voice. It is compromised of six cartilages that create its shape. These include three unpaired (only one):- Cricoid Cartilage
- Thyroid Cartilage
- Epiglottis
And three paired cartilages:
- Arytenoid Cartilages
- Corniculate Cartilates
- Cuneiform Cartilages
These can be seen in the image below:
These cartilages work to both protect the vocal folds and help with movement to alter pitch and loudness.Several muscles are contained both within and outside of the larynx that help move the structures and vocal folds as well. The internal muscles can be noted here:
Let's watch a video showing some movements the larynx and vocal folds can make when we produce varying pitches and speech sounds:
We can see how the vocal folds are pulled taut and thinner to create higher pitches, and brought together and made "fatter" to create lower pitches.
When pitch is measured, it is referenced in a number form in Hertz, abbreviated Hz, and is what is perceptually heard from the fundamental frequency (f₀) of the vibration (a future post).
The Vocal Tract
The vocal tract, as we've mentioned, is the structures above the larynx that alter the quality of the sound produced by the vocal folds within the larynx. Here is a basic illustration of what the vocal tract includes:
So, all the tissues of the throat, mouth, and nasal cavity have an effect on the sound waves produced by the vibration of the vocal folds. Larger cavities or spaces within the vocal tract tend to produce more "robust" or "rich" qualities, while smaller spaces create more "bright" or "pinched" qualities. This, along with pitch, is one of the fundamental ways voices can sound masculine or feminine. Biological males have larger vocal tract cavities than females, and thus produce more resonant voices.
Resonance
Resonance is how the vibration of the vocal folds through the vocal tract becomes "filtered". It can be defined as
"the process by which the basic product of phonation is enhanced in timbre and/or intensity by the air-filled cavities through which it passes on its way to the outside air."
- McKinney, James (1994) The Diagnosis and Correction of Vocal Faults, Nashville, TN: Genovex Music Group.
The three most important resonating chambers of the vocal tract can be observed in the image above, and include the pharynx, oral cavity, and nasal cavity.
The shaping of these chambers effects the frequency of vibration of the sound wave and thereby changes the perceived sound we hear. This is how we can perceptually tell the difference between the various vowel sounds, whereby only the shape of the vocal tract is altered and no articulators (e.g., tongue, teeth, lips) are utilized.
We can measure the frequencies of the various vowels using a spectrograph which produces the picture below, called a spectrogram. Vowels are composed of formants, or acoustic resonances of the human vocal tract. Vowels can generally be distinguished by hearing the first two formants. We can see what frequencies these formants are located on the following spectrographic display of the vowels /a/, /o/, and /u/:
I always find it amazing how quickly our auditory system can pick up on changes in the frequency of sound waves to help us decipher the various speech sounds. When we consider that a sound wave begins at the level of the vocal folds, travels and is filtered through the focal tract and air, picked up by our auditory system, and processed by the auditory and speech centers of the brain to decipher meaning, it's amazing we can keep up with conversation!
In the future we will go more in depth with some of the science above, particularly formants and resonance, when we talk about altering the speech signal to affect the quality, or timbre of the voice. Please join me again next time, and thank you for reading! If you have comments or questions please share below!
The shaping of these chambers effects the frequency of vibration of the sound wave and thereby changes the perceived sound we hear. This is how we can perceptually tell the difference between the various vowel sounds, whereby only the shape of the vocal tract is altered and no articulators (e.g., tongue, teeth, lips) are utilized.
We can measure the frequencies of the various vowels using a spectrograph which produces the picture below, called a spectrogram. Vowels are composed of formants, or acoustic resonances of the human vocal tract. Vowels can generally be distinguished by hearing the first two formants. We can see what frequencies these formants are located on the following spectrographic display of the vowels /a/, /o/, and /u/:
I always find it amazing how quickly our auditory system can pick up on changes in the frequency of sound waves to help us decipher the various speech sounds. When we consider that a sound wave begins at the level of the vocal folds, travels and is filtered through the focal tract and air, picked up by our auditory system, and processed by the auditory and speech centers of the brain to decipher meaning, it's amazing we can keep up with conversation!
In the future we will go more in depth with some of the science above, particularly formants and resonance, when we talk about altering the speech signal to affect the quality, or timbre of the voice. Please join me again next time, and thank you for reading! If you have comments or questions please share below!
