Sing as you Like!

When it comes to how the voice sounds, there are only 3 components:

1. The Breath
2. The Sound Source
3. The Resonators

Component 1: The Breath

When we exhale, air passes through our vocal cords.

This is necessary but insufficient to create our sound.

If we don’t exhale, we don’t get any sound.

If we exhale while the vocal cords are fully apart, there is little to no sound.

It is only once we bring our vocal folds together while exhaling that we start the vibration of the vocal folds.

Component 2: The Sound Source

When the vocal folds are brought into vibration, they create a fundamental frequency and multiple overtones.

The intensities (loudness) of these overtones create a slope that looks something like this:

This is known as a spectral slope. It just sounds like a buzz.

The thicker the vocal folds are and the closer they are together, the gentler the slope. For example, if you sing with a loud, strong voice, the slope might look like what you see above.

The thinner the vocal folds are and the further apart they are, the steeper the slope. For example, a soft, light voice might have a slope that looks like this:

Each harmonic provides its own unique vowel colour. Lower harmonics sound more like “oo” (as in “choo choo”). They then start to sound more like “ah” (as in “father”) as they get higher. Eventually, the harmonics start to sound like “ee” (as in “keep”).

Component 3: The Resonators

When these overtones pass through our vocal tract (everything above the vocal folds), different harmonics get muted or emphasized. The frequency of harmonics that will be emphasized is called a resonance frequency (you may also hear the term “formant frequency”, which is almost the same thing).

The vocal tract can be thought of as one long tube from the vocal folds to the mouth. When we move our tongue, jaw, lips or larynx around, we can split the vocal tract into more tubes. If we lower the soft palate to allow sound into our nose, we get yet another tube (the nasal cavity).

For each of these tubes, the shorter the tube, the higher the harmonics that are emphasized by that tube. The longer each tube, the lower the harmonics that are emphasized by that tube.

Due to the phenomenon of Helmholtz Resonators, lower harmonics might also be emphasized if particularly small narrowings are created in the vocal tract.

The harmonics that are emphasized determine what vowel you hear.

For example, this is an “ee” vowel, created by a high and forward tongue. Very low frequencies (“oo”) and very high frequencies (“ee”) combine to form what we hear as “ee”:

On the other hand, an “oo” vowel, created with a high backward tongue and rounded lips, looks like this, where only low “oo” sounding harmonics are emphasized:

The harmonics that are emphasized also play a role in whether we consider a sound to be “bright”/”forward” or “dark”/”backward”. If higher harmonics are emphasized, we call that “bright”. If lower harmonics are emphasized, we call that “dark”.

Resonance is responsible both for the vowels we hear and the quality of that sound.

For example, lowering the larynx creates a “darker” sound, because it lengthens the entire vocal tract, thereby lowering all resonant frequencies.

Using a vowel that has a higher first resonance frequency also tends to make the sound appear to be more powerful (some might say “chesty”). If one tunes the second resonance frequency to any harmonic, they can also create a ringing quality to the sound.

It is worth noting that resonances will be easier to hear with a gentler spectral slope, as there will be more harmonic content to be filtered.

Final Note: Non-Linearity

It must be noted that these three components all affect each other. In a sense, there is a feedback loop that makes this breath-source-resonator model one that is “non-linear” or dynamic.

For example, when singing with a higher first resonance frequency, not only does the final sound seem more powerful, but the vocal folds will tend to come together more tightly.

When one tunes their harmonics with their resonance frequencies, the vocal folds also come together more easily, especially when the first resonance frequency is kept low.

In both of these examples, the resonator affects the sound source.

When one pushes more breath pressure, the vocal folds also tend to get tighter to hold the air back, which affects the spectral slope. In this example, the breath affects the sound source.

Conclusion

You now have a broad overview of the acoustics of the voice. Any technique adjustment aimed at improving the sound of your voice (as opposed to its efficiency) must be critically examined in terms of what it can do in the context of the breath-source-resonator model outlined above.

The above only broadly covers the physics of why you sound the way you sound. Nothing has been mentioned about how to manipulate the breath, sound source and vocal tract to produce the sounds that you want. These will be covered in future blog posts, so stay tuned!