Learn to Sing: What is Resonance in Singing?

Vocologists use voice science to rehabilitate voices. Voice science is constantly evolving but is essentially fact-based. Vocal pedagogy varies widely and are often based on tradition.

Vocology is: the science and practice of vocal habilitation. Its concerns include the nature of speech and language pathology, the defects of the vocal tract (laryngology), the remediation of speech therapy, and the voice training (voice therapy) and voice pedagogy of song and speech for actors and public speakers. Vocologists are science-based in their approach to teaching singing.

Pedagogy is: the method and practice of teaching, especially as an academic subject or theoretical concept. Vocal pedagogy has historically embraced both scientific and non-scientific approaches to teaching singing.

In vocal pedagogy, the concept of resonance has come to have many meanings, some science-based and some perception based.

Here, we will discuss the voice science approach to how resonance really works, and then we will explore some of the sensation-based interpretations of resonance that abound in vocal pedagogy.

HOW RESONANCE WORKS

There are two types of resonance. They are known as sympathetic resonance and conductive resonance.

1. Sympathetic (free) Resonance: Sympathetic resonance occurs when there is no physical contact between two bodies, but the second resonator responds sympathetically to vibrations received through the air from the first. Sympathetic resonance is created in an object or person in close proximity to the source, but not connected to the source.

A glass shattering as the result of an extremely powerful high note is an example of sympathetic vibration. Another example would be a piano string vibrating one octave higher than the string that was struck.

Singers experience sympathetic vibration in the chest cavity when singing low notes. The chest cavity vibrates in response to lower pitches because of its larger size.

Some singers feel a vibration in the head when singing high notes.  The cavities of the head vibrate sympathetically in response to higher pitches due to their smaller size.

2. Conductive Resonance: Conductive resonance occurs when the resonator has contact with the vibrating body. A violin operates by conductive resonance: the vibrations travel through the bridge of the instrument to the body of the instrument through the string by direct contact. Vibrations traveling through cartilage, bone, and muscle are absorbed by the tissues of the body, so the body is not a good agent for conductive resonance.

When sound waves are introduced into an air-filled cavity, the structure will tend to boost some frequencies while attenuating or damping other frequencies selectively as a function of the shape, size, and composition of the walls of the cavity and shape of the opening.

Larger containers boost lower frequencies; smaller containers boost higher frequencies.

Think of blowing air across bottles of various shapes and sizes. Each bottle will produce a different pitch as that bottle selectively reinforces frequencies that match its dimensions and attenuates (damps by comparison) frequencies that do not match. This is the filtering process of resonance.

Some resonators are selective, responding only to certain frequencies, and some resonators respond to a broad range of frequencies. Frequencies traveling through a cylindrical resonator are affected by the length of the tube, which determines the distance sound waves must travel. Softer surfaces tend to absorb sound.

The pharynx is a fairly soft cylindrical resonator that can assume various lengths depending upon the positioning of the larynx. The oral cavity or mouth is a combination of soft and harder areas and assumes different shapes depending on the positioning of the jaw and tongue.

When two or more resonators are joined together, the resonators affect one another. The pharynx and mouth function in this manner, each potentially affecting to some degree the resonance of the other.

The pharynx and mouth are resonators or containers that can be adjusted by movements of the tongue, jaw, soft palate, and lips, all of which affect the size of each container. The soft tissues of the pharynx and mouth can further affect vocal quality when they are tensed or relaxed.

Singers differ physiologically in the size of the pharynx, mouth, and tongue. This inherent difference in size is one element contributing to the uniqueness of each singer’s voice. Singers can also position the tongue, jaw, and lips to alter the shape of the resonators, thereby selectively boosting some partials and attenuating or damping out others.

RESONANCE IN SINGING

Resonance in singing can be described as the process of turning aerodynamic energy into acoustic energy.

Air meets the bottom of the folds and is first resisted and then released from the top of the fold.  This energized air contains various frequencies that pass through the pharynx and mouth and are filtered.

Here’s how it works: a vibrational wave occurs in the vocal folds as air causes the folds to rapidly open and close, converting air into frequencies known as partials. Some of these partials are reinforced or boosted in the pharynx and mouth cavities and others are attenuated or damped through a process of filtering.

The fundamental frequency (F₀) is perceived by the listener as pitch. When you sing the A above middle C, for example, the fundamental frequency is 440 Hz. That means the vocal folds opened and closed 440 times.  But our ears are not only hearing the fundamental; we are also hearing many other frequencies generated along with the pitch. These are known as overtones.

Harmonics are partials or overtones whose frequencies are multiples of the fundamental frequency. The relative strength of various harmonics provides tone color or timbre.

PERCEPTIONS OF RESONANCE

The terms resonance and register are sometimes confused.

Registration refers primarily to vocal fold activity: short thick folds, heavy mechanism, modal or lower register, chest voice, or mode 1 vs. long, thin folds, light mechanism, upper register, head voice, or mode 2.

Resonance refers to the filtering of the basic voiced sound where certain partials are boosted and others attenuated.

However, registration and resonance affect one another.

Sensations experienced during singing have, over time, generated terminology that is misleading because it is based on subjective experience rather than science. Singers typically feel vibrations in the chest cavity while singing low notes and consequently refer to lower pitches as their chest voice or chest register.

However, the voice is not resonating in the chest cavity; what they are feeling is known as sympathetic resonance as the larger cavities of the chest vibrate in response to lower pitches.

True resonance (the filtering and boosting or attenuating of partials) occurs above the vocal folds, in the pharynx (throat) and mouth.

EXPERIENCE IT- SYMPATHETIC RESONANCE

Place your hand on your chest and energetically say aaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhh!

You will feel a vibration in the chest. This vibration is the basis for the evolution of the terms chest voice and chest register. Your voice isn’t being produced in the chest, but you feel vibrations there. The chest cavity (thorax) is actually not a good resonator because it contains many organs, the tissues of which tend to absorb sound.

Next, place your hand on the back of your neck and say weeeeeeeeeeeeeeeeee! on a high pitch. You will again feel a vibration under your hand. But your high voice is not produced in your head, either.

The terms head voice and chest voice refer to sympathetic resonance experienced by the singer. Lower notes cause the larger chest cavity to vibrate sympathetically, and higher pitches cause the smaller head cavity to vibrate sympathetically.

RESONANCE TRANSFER AND SPLIT RESONANCE

When singing low to high pitches, singers may notice a feeling of resonance transfer as the pitch ascends. In the lower notes, the resonance appears to be traveling straight out of the mouth. On the highest pitches, the sound might appear to be traveling out the back of the head.

In the middle of the range, there is an area in which the singer feels the resonance not only hitting the hard palate and traveling outward (as it appears to do on lower pitches), but also behind the soft palate (as it appears to do on higher pitches). This is the perception of split resonance that singers experience in the mix.

The image below depicts what the transfer of resonance sensation feels like to a singer vocalizing  low to high pitches. The lower notes seem to travel straight out of the mouth as in speech production. In the middle notes, there is a perception of split resonance; some of the resonance feels like it is traveling out the mouth and some like it is behind the soft palate.

This is the feeling singers experience as they enter the first bridge or primo passaggio and begin to mix. As the pitch continues to ascend, the highest pitches begin to feel to the singer as if they are transferring behind the soft palate and resonating in the head.

For sensation-based singers, concepts based on subjective experiences such as split resonance and resonance transfer can be helpful. While they may not be scientifically accurate (at least as causational phenomena) these concepts can assist the singer in identifying what good vocal production feels like in the body, since we cannot see what is happening in the vocal tract.

The singer’s perception of resonance transfer and split resonance can be tremendously enlightening imagery.

This experiential, perception-based approach might be a good adjunct to a science-based approach.

EXPERIENCE IT: SYMPATHETIC RESONANCE- THE SIREN

This exercise will help you feel what it is like to sing from the bottom of your voice to the top of your voice in one unbroken line. Perform a siren, vocalizing from your lowest note to your highest note on an [i] vowel. Now try it on the [æ] vowel. See if you can smoothly transition from your lower register to your upper register with no breaks or abrupt changes in quality.

Can you feel the sound vibrating in your chest area to start, then vibrating in the front of the face, and finally shifting to your head, as pictured in the image below?

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