|MadSci Network: Genetics|
Before I answer your question, let�s first talk about some anatomy. For producing the sounds that make up the human voice, the larynx is the hot spot. It is a walnut-shaped structure that sits at the top of the trachea (the windpipe that leads to the lungs) and there are several neighboring muscles and cartilages that are associated with it. The larynx also houses the vocal folds, more commonly known as the vocal cords, which are two rubber band-like structures that generate the sounds that comprise the human voice. Structurally, though, the vocal folds are much more complex than rubber bands � they are elegant, multi-layered structures composed of connective and muscular tissues.
In general, voice qualities are determined by the vocal folds (how tautly they close and how symmetrical they are) as well as their surrounding structures, including the size of the larynx and the strength of the nearby muscles.
Scientists are actively studying the genetics of voice, particularly as it relates to various vocal disorders. While the details are not yet fully understood, it seems likely that genetics plays a role in determining some aspects of voice quality. Just like other parts of your body, genes sculpt the various tissues that influence voice quality, including the larynx, the vocal folds and the surrounding muscles. Since you share many of your genes with your siblings, parents and other family members, you likely have some similar structural features in these voice-producing components, which contribute, in part, to your similar voices.
But, genetics is only part of the story. As you mentioned, hormones influence voice quality, which often surfaces during puberty. There are also many environmental factors that can influence the voice. For example, children hear the voices of their parents, which in turn, can affect their own voices. This often occurs with regional accents, such as the ones heard from some Bostonians or from some native New Yorkers. There are things in the air, such as inhalants (pollution, for example) or infectious agents, which can affect the vocal folds, resulting in voice changes. Some medications can also affect the voice. Finally, constant use of the voice for long periods of time, like singing (opera singers, rock singers) or lecturing (teachers) can strain the vocal folds and cause noticeable changes in voice quality.
With many of these environmental factors, it is not unusual for members of the same household to be exposed. And because family members often live together, these external influences can similarly affect their voices.
Therefore, it seems likely that an interaction between genes, environment and frequency of use determine the nature of the voice, though it is not yet clear how much each factor contributes.
I hope this information is helpful!
The Human Vocal Fold
This site has information on the physics of sound production related to the voice and the vocal folds.
Voice Academy: Science Center
An educational tool from the National Center for Voice and Speech
Try the links in the MadSci Library for more information on Genetics.