Vocal range is determined by the size of the thyroid cartilage.

Vocal range is classified and measured by listening to the type of voice a person possesses, such as soprano, alto, tenor baritone or bass.
Of course, the condition is also important when determining the vocal range by singing.
I often hear the following statements: “I wanted to sing soprano, but my teacher said that I’m a mezzo-soprano.” or “Although I thought my voice sounds baritone, the vocal coach said that my voice sounds more in the range of bass.”
If your teacher or vocal coach observes your singing range and classifies it by name, that decision should be trusted as well as accurate.
However there is another way to determine a person’s vocal range, and that is by the size and shape of the thyroid cartilage.
Vocal range is decided by the size, the angle, the thickness/width of the thyroid cartilage, and also the size and shape of the hyoid bone.


(This view is from directly above the hynoid bone, the thyroid cartilage, the arytenoid cartilage, and the cricoid cartilage.)
For example, when you see the viola and violin, the size is obviously different. The style has similarities, but the range of sounds that can be produced are very different.

(The left is a violin and the right is a viola.)

Vocalization is really similar to and can be compared to musical instruments. My studies and experience have given me the ability to know what kind of vocal range is suitably associated to a person by visually examining their larynx.

Note: Technically the soft tissue around the thyroid cartilage also relates to deciding vocal ranges.
Also, the resonance chamber plays an important role in the determination of vocal range. In the fact, these parts can be exercised and strengthened through training and practice, making them relevant to athletic ability. In conclusion supporting the association between vocalization, musical instruments and sports.
As mentioned in the 5 factors of Creating Voice (Please see the top page in the blog), vocalization is made by “Physical movements”,” Practiced techniques” and “Mental health”. Focus on these areas when finding a suitable song to match with your vocal range. Finding the correct type of sound to match your abilities will utilize the skill range of your overall voice.