It is hardly news that singers monitor their voices by feeling, as much as by hearing. For the listener, the voice is what comes out of a singer’s mouth. For the singer, however, the voice is also a vibration, a physical resonance, which is probably what makes the voice the most personal of all instruments. This column will look at how the voice is “felt,” and the ramifications of this important biofeedback mechanism in various situations.
So, if you will bear with me through a bit of science, may I have the first slide, please.
Sound begins as a mechanical vibration that travels through the air, resulting in either a single disturbance (such as an explosion), or as a series of waves (tones). When these waves stimulate the ear, they are transformed into electrical impulses. The brain then interprets these electrical impulses as “sound” (which answers the old question of the tree falling in the forest: If no one is there to hear it, it really doesn’t make a sound!) By convention, though, we will continue to refer to these mechanical waves as sound waves.
We usually think of sound waves as traveling through air, but they also travel through other media, such as water, metal—and the soft and bony tissues of the body. When sound waves travel through the body, we feel and hear them. We feel the mechanical vibration of the tissues by proprioception, and we hear the waves that reach the inner ears by bone conduction. Therefore, you perceive your voice in three ways: as an external sound heard through the air, an internal sound conducted through the skull, and as vibrations felt in different parts of your body.
A singer performs by real-time biofeedback: adjusting the voice based on the almost-simultaneous perception of body vibrations, bone-conducted sound, and the actual voice coming out of the mouth and traveling to the ears. Even that is not the whole story. Singers have a fourth modulating input: the perception of muscle tension in the vocal apparatus. This is not vibration, but the pull of the muscles that tighten the vocal folds and the walls of the vocal tract.
Sound conduction through the body is not a simple linear process. The head and chest contain amplifiers and dampers that affect the voice. Some sound (ideally, a lot of sound!) is reflected from the surfaces of the upper airway, and soars through the mouth toward the back seats of the theatre.
How much sound? That depends on many factors, including the absorptive qualities of the surfaces (hard or soft), the angle of deflection, wave reinforcement and cancellation, and so on. The various open and closed cavities—pharynx, sinuses—which resonate at specific frequencies, amplify the voice and make it louder. But sound intensity is also lost at the interface between different media, such as between air and bone (the walls of the sinuses), and between soft tissue and bone (the lining of the pharynx, mouth, and nose). So the sinuses both amplify (by resonating), and dampen (by losing energy as it crosses from one medium to another) bone-conducted sound.
What are the practical implications for the singer?
First, the role of the sinuses, always a point of debate, is probably negligible. You may gain some sound by resonance, but also probably lose sound as it travels back and forth across the sinus walls, from bone to air and back again. Sinus resonance probably has a greater effect on how you hear your own voice (through the skull), than on what actually comes out through your mouth.
The same goes for the nasal passages. Although many patients have told me that after surgical correction of a nasal septal deviation their voice “sounds bigger,” I think this is more a matter of self-perception than a true change in what the audience hears. I do believe, however, that enlarging the vibrating cavities of the nose by surgery may put the voice into a different space, and may make it easier for singers to place the voice in the mask correctly. The voice may sound “bigger,” in the sense of less nasality and constriction, rather than actual loudness.
Second, the paradox of “sounding better” with a cold. When you have a cold, the mucous membranes lining the vocal tract are swollen, softer and thicker. They absorb more of the voice you generate. The voice therefore sounds richer and louder to you (by bone conduction). The sad truth, however, is, that less comes out of your mouth, so the audience hears a sound that is actually softer and less brilliant.
Most importantly, in some situations a singer cannot hear the sound she or he is producing, and becomes critically dependent on monitoring through skull vibration. This occurs in choral singing, where you hear only the voices to your left and right, not your own. Singing at an outdoor concert, or pop singing with microphones but no monitor speakers, has a similar effect.
As you try to adjust the voice, bone conduction of sound and vibration necessarily overrides what you actually hear. The usual strategy of synthesizing the information provided by vibration, bone conduction and ear-perception fails, and the singer often has to “fly blind,” that is, rely on bone-conducted vibration, and monitor muscle tension in the vocal tract. Oversinging and vocal damage can result.
This phenomenon may also explain in part why some singers are habitually sharp or flat: Singing by feeling, rather than sound, dominates in the biofeedback process.
Disclaimer: The suggestions given by Dr. Jahn in these columns are for general information only, and are not to be construed as specific medical advice or advocating specific treatment, which should be obtained only following a visit and consultation with your own physician.
