Nasal voice is a descriptive term given to a speaking voice that has a noticeably nasal quality to it. The nasal quality is caused by an incomplete or weak closure of the velum, which is an anatomical structure located in the back of the mouth that is used to separate the oral cavity from the nasal cavity. A nasal voice may be a sign of a weak velum, or it can be caused by an anatomical variation that precludes the ability to tightly close the velum. It can also be the result of a learned speech variation.
The sounds of speech are divided into nasal and non-nasal sounds. Nasal speech sounds are those produced with air moving through both the mouth and the nose, or in more technical terms, both the oral and nasal cavities. In English, the vast majority of speech sounds are non-nasal, which means they are produced with air flowing through the mouth but not through the nose. The small subset of English nasal speech sounds that are always produced with air flowing through the nose include "m," "n," and the "ng" sound that occurs at the end of words such as king.
Typically, when a person produces a non-nasal speech sound, air flows through the mouth only. If air is allowed to flow through the nose during the production of non-nasal speech sounds, the resulting voice is referred to as hypernasal speech or nasal voice fix. This occurs when there is incomplete closure of the velum, which separates the mouth from the nose. The velum is a muscular structure that can be raised to make contact with the back of the throat, also known as the pharynx. Incomplete closure can also occur in cases of cleft palate or when there is an opening known as a fistula in the palate, which is the anatomical structure at the roof of the mouth.
When complete closure of the velum is achieved, the nasal quality of speech is eliminated. A person who has a nasal voice does not achieve complete closure the velum during speech. There are several reasons this may occur. Some people are unable to close the velum due to genetic variations in anatomy such as a short velum or an enlarged pharynx. Others may have a weak velum that cannot be raised high enough to achieve complete closure. In some cases, a partial blockage of the pharynx can make it impossible for the individual to achieve closure, and in still other cases, the person is capable of raising the velum but has learned to speak with a nasal quality.
Some individuals who have a nasal voice seek therapy to decrease the nasal quality of their speech. Nasal voice therapy includes exercises to strengthen the velum. Speech prosthesis, which are also referred to as dental plates, can also be used to bring the velum closer to the pharyngeal wall so that less muscular action is required to close the velum completely.
For some individuals, variances in anatomical structure preclude the ability to correct nasal voice without surgery. Nasal voice surgery may involve an attempt to elongate the velum so that it can make contact with the back of the throat, or it may involve an attempt to bring the walls of the throat directly behind the velum closer to the velum in order to improve contact between the velum and the pharyngeal wall. If there is a fistula in the palate, surgery will involve closure of the opening.
