Singing Better: Formants

Resonance, in voice science, occurs in the vocal tract and refers to the relationships between harmonics and an elusive concept called formants.

What are formants?

There are many varied definitions of formants in singing. My favorite one is simply a formant is the pitch of the vibrating air in a container. (voicescienceworks.org)

The “containers” in singing are the mouth and pharynx in the singer’s vocal tract. Our containers or resonators (the mouth and pharynx) have preferred resonance frequencies based on their size, shape, density, and opening. These preferred frequencies are known as formants.

Here are some other definitions of formants:

A formant is a peak in the sound spectrum.

Or: A formant is a resonance of the vocal tract and is a physical property of the vocal tract.

Or: Formants are the range of frequencies in which sound is maximized.

Or: Formants are the range of frequencies the resonator spaces of the pharynx and mouth can most effectively amplify in the vocal tract, measured as an amplitude peak or boost in frequency when a singer sings into a spectrogram, an electronic device that measures peaks in the harmonic spectrum of the voice during singing.

Or: Formants are the range of frequencies or pitches at which the air in a container vibrates most efficiently.

Or: Formants are the ranges of frequencies at which stronger amplification occurs- the frequencies the vocal tract responds to the most.

Or: Formants are the range of frequencies a container of a certain size can most effectively resonate.

Or: Formants are vibrations of the air inside the vocal tract- the pharynx and mouth. These pockets of air vibrate at preferred frequencies determined by the size and shape of each container and the size of the container’s opening. So, dropping the jaw, for example, affects the opening of these containers, and thus the formant frequencies in those containers.

When a formant and a nearby harmonic synchronize due to the shape of the resonators as we sing vowels there is an increase in energy; this has traditionally been called resonance.

WHERE ARE THE FORMANTS?

The vocal tract produces many formants, but the first five, F₁-F₅, are the most relevant in singing.

Vowels are comprised of various combinations of F₁ and F₂. Although many formants can be active to some degree when we sing, the two lowest formants, F₁ and F₂, are the most active, working together. One formant will be dominant, more actively resonating nearby harmonics.

F₃, F₄, and F₅ produce the phenomenon known as the Singer’s Formant, the extra ring in a voice that allows it to be heard over loud accompaniments such as an orchestra or rock band.

The frequency location of a formant is based on the length and shape of the tube known as the vocal tract. One rule to remember: smaller spaces boost higher frequencies and larger spaces boost lower frequencies. 

So, the size of the container determines whether high or low frequencies resonate there. A longer tube means lower formant frequencies will resonate there. A shorter tube means higher formant frequencies will resonate there.

The two resonating chambers or containers are the pharynx (longer tube) and the mouth (shorter tube).

Formants for men, women, and children are different because of the difference in resonator size; for example, women’s formants are 10-15% higher than are men’s. Children’s formants are higher still due to the smaller size of the pharynx and mouth.

Men, because of their longer resonating containers, show more formants active during singing; women, with a 20% shorter vocal tract, show fewer active formants

The first formant is the frequency or pitch of the air in the container that extends from the constriction of the tongue to the vocal folds. This area is the pharynx. It is the larger of the two containers.  The pharynx container boosts the lower frequencies because it is larger.

The second formant is the frequency or pitch of the air in the container that extends from the  constriction of the tongue to the lips. This area is the mouth. It is the smaller of the two containers.  The mouth container boosts the higher frequencies because it is smaller.

Although they are always working together, F₁, the first formant, resonates most effectively in the larger space of the pharynx, which boosts the lower frequencies most effectively. F₂, the second formant, resonates in the comparatively smaller space of the mouth, which more effectively boosts the higher frequencies.

F₁ contributes to oscuro, or darkness/depth in tone quality, rather like the bass EQ on a stereo. F₁ frequencies range roughly between 250 Hz and 1000 Hz (C4-C6) depending on the vowel (and the size of the person singing that vowel).

F₂ contributes to squillo, or treble/brilliance in the sound, like the treble EQ on a stereo. F₂ frequencies range roughly anywhere between 600-800 Hz and 2200 Hz (D5-C7). F3-F5 range from 2200 Hz to 3200 Hz. (Db7- F#7).

THE VOWEL FORMANTS F₁ AND F₂

The first two formants, F₁ and F₂, respond to changes in the shape of the vocal tract and are known as the vowel formants. Because we can change the shape of our vocal tract, we can tune or adjust these vowel formants.

Even when two people are speaking the same language there is often an enormous difference in the way they pronounce vowels. There is a noticeable difference in the spoken AH sound, for example, in the phrase park the car when pronounced by a Southie Bostonian, as compared to someone who grew up in California.

This is due to differences in shaping the vocal tract- the tongue, larynx height, lips, and soft palate.

Think of the vocal tract as divided into “rooms”- a back room (the pharynx) and a front room (the mouth) with the lips being the front door (open or closed). The room divider is the constriction or hump of the tongue.

F₁ frequencies resonate in the back room (pharynx), and F₂ frequencies resonate in the front room (mouth). They resonate at the same time, but one room or the other will have more energy at any given time.

A very specific combination of two formants- F₁ and F₂– is required to create recognizable vowels. Now, remembering our maxim of small container/high pitch, large container/low pitch, we can see how formant frequency is affected by the changing size of our “rooms” as the tongue moves from high to low and from front to back to form vowels.

When we have a small “front room,” (the mouth) we will have higher F₂ frequencies. Because the “back room,” the pharynx is now larger, due to the tongue position, it will resonate the lower F₁ frequencies. This is the resonator shape of the [i] vowel: 300 Hz F₁ and 2500 Hz F₂.

When singing or speaking the [i] vowel:

The pharynx (F₁– behind the tongue constriction) is large, and so the formant frequency (pitch) is low. F₁ for [i] is 300 Hz.

The mouth (F₂-in front of the tongue constriction) is small, and the formant frequency (pitch) is high. F₂ for [i] is 2500 Hz.

[i] is a closed vowel- this means it is formed with a high tongue. F₁ and F₂ are far apart in frequency.

However, in the [ɑ] vowel F₁ and F₂ frequencies are closer together. This is because [ɑ] is formed with a flat tongue and the “rooms” are more similar in size.

When singing or speaking the [ɑ] vowel:

The pharynx (F₁– behind the tongue constriction)) is smaller than it was for [i] and so the pitch of the vibrating air is higher than it was for [i]. F₁ for [ɑ] is 725 Hz.

The mouth (F₂-in front of the tongue constriction) is larger than it was for [i] and the pitch of the vibrating air is lower than it was for [i]. F₂ for [ɑ] is 1100 Hz.

[ɑ] is an open vowel- this means it is formed with a low tongue.

THE FIRST FORMANT F₁

F₁ frequencies are always lower than F₂ frequencies. In the front vowels, [i], [ɪ], [e], [ɛ], [æ], F₁ and F₂ start out spread quite far apart, and gradually come closer together.

F₁ determines depth, roundness, warmth, fullness of timbre (oscuro), by strengthening the lower harmonics.

F₁ is related to tongue height: High tongue=closed vowel=low F₁=more release in singing. Low tongue=open vowel=high F₁=more hold in singing.

First formant frequencies are generally between C4 (261 Hz) and C6 (1046 Hz). Since vocal tract sizes vary, each person’s first formant frequency when singing the same vowel will be different. Men will be lower due to their larger larynx size, women will be a bit higher, and children higher still.

The tongue is the divider separating the pharynx and mouth resonators. The tongue constriction or hump changes from high and forward for the vowel [i], a closed vowel, (closed means the tongue is close to the teeth or hard palate) to progressively lower positions for the successively more open vowels like [ɑ].

As the tongue moves from high to low (from closed to open vowels), the pharyngeal cavity decreases in volume or space, and the mouth cavity (meaning the area in front of the tongue constriction) increases in volume or space.

F₁ correlates inversely with tongue height; the higher the tongue is, the more closed the vowel is and the lower F₁ frequency is, because the pharyngeal container is comparatively larger.

Closed vowels, because the tongue is high in the mouth and pulled upward and out of the pharynx, create more pharyngeal space and less mouth space. Closed vowels with lower F₁ correlate with less chestiness or less weight, and therefore, more release.

Vowels that require a smaller mouth opening at the lips, like [u] are also correlated with lower F₁ because they lengthen the resonator, increasing the size of the container.

A larger mouth opening, by widening the lips or dropping the jaw, creates a smaller pharyngeal container and thus higher F₁ frequencies.

Singers who belt, singing pitches above the first bridge in the chest voice, always evidence a wide grimace with extremely spread lips and a raised larynx, which increases F₁ frequencies as the pharyngeal container becomes smaller.

Belters tend to sing high notes primarily on open vowels because F₁ frequencies are intrinsically higher. They generally prefer a flattened tongue, again because the flatter the tongue position is, the higher F₁ frequencies are.

F₁ is like the bass knob on a stereo, affecting depth, or oscuro.

 F₁ raises as the pharyngeal cavity size (the distance from the larynx to the hump of the tongue) is decreased; this is what happens when the larynx lifts- the distance from the larynx to the tongue constriction decreases, and F₁ frequencies are raised.

Lifting the larynx and widening the lips contributes to "pulled chest", the hallmark of the Unbalanced/Pulled Lower category singer.

When the mouth cavity size is increased, (when we drop the jaw) or lip aperture is increased (when we spread the lips), pharyngeal resonating space is comparatively decreased as mouth space is increased, raising F₁ frequencies.

Rounding the lips and pushing them forward increases the length of the resonator and decreases the opening, lowering F₁ frequencies. A rounded, forward lip position can create less hold and more release.

If you have a tendency to strain at the transition through the first bridge, round your lips.

Belters sing with a raised larynx, a flat tongue, and a wide mouth, which creates a smaller pharyngeal space. This raises F₁. Protruding the lips lowers F₁, preventing pulled chest.

THE SECOND FORMANT F₂

The second formant, F₂, (resonating in the “front room”- the mouth) is determined by how forward or back the tongue is. It provides vowel definition and clarity. The frequencies of the second formant are between A5 (880 Hz) and D7 (2349 Hz).

In the back vowels, [ɑ], [ɔ], [ʊ], [o], [u], F₁ and F₂ are much closer together, because as the tongue (or where the vowel is formed on the tongue) moves from front to back, F₂ decreases in frequency.

When F₂ is lower, it is closer to F₁; because of this proximity, it boosts F₁. F₁, in turn, boosts the lower frequencies, kind of like a bass knob on a stereo. So that’s why back vowels seem darker.

F₂ is correlated with the front-to-back position of the tongue; moving the tongue forward raises F₂ and retracting the tongue lowers F₂.

F₂ is like the treble knob on a stereo, affecting brilliance, or squillo.

Front Vowels

Moving the tongue forward to form front vowels raises F₂.

When the distance from the tongue constriction, or hump of the tongue, to the lips is decreased, F₂ is raised. The front vowels [i], for example, a closed vowel made with a high and forward tongue, and [æ], created with a low and forward tongue, both have high F₂ and are used to add brilliance when training voices.

Back Vowels

Retracting the tongue lowers F₂.

Vowels made with the tongue further back in the mouth are called back vowels; these vowels have much lower F₂ frequencies than the front vowels do. Front vowels create brilliance; back vowels do not.

F₂ frequencies decrease as the front resonating cavity is enlarged because of tongue retraction or lip protrusion (less treble).

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