5.11: Sound Production

The vocalizations produced by people involve words and a variety of other sounds, such as moans, grunts, whistles, cheers, and laughing. People use sound production for communication. Communication among individuals by sound and other means (e.g., visual signals) is important to a high quality of life and to survival because it is one of the three components in negative feedback systems. A common example of using vocalization as part of a negative feedback system is shouting a warning to a person in danger.

Human sound production can enhance life in other ways. Words and other vocalizations can motivate and encourage positive actions such as beginning a new career or hobby. They are also used in teaching, praising, consoling, expressing emotions, and many other human activities. And what of the beauty of a poem or a song? All these are created by the sounds produced by the flow of air through airways.

Mechanisms

The respiratory system produces sound by passing air through the upper airways and the mouth. Most of the sound people make is caused when air passing through the larynx causes the vibration of two flaps of tissue called the vocal cords (Figure 5.5). The sound gets louder when more air flows through the larynx.

Different muscle contractions in the larynx control the position and tension of the vocal cords and thus alter the pitch of sounds. The sounds made by the vocal cords are modified by the other upper airways, especially the nasal passages and the mouth. By changing the shape of these passages and moving the tongue, a person can create a multitude of sounds and form words.

All the actions that produce and modify sounds from the respiratory system are controlled by the nervous system.

Age Changes

Many age changes that alter inspiration and especially those which modify expiration affect sound production. Age-related stiffening of the larynx, shrinkage of the vocal cords and its muscles, and changes in the mouth are also important. Age changes in the nervous system are also important since sound production depends on the coordinated action of many muscles. Even age changes in hearing are important because the ears provide feedback information so that the sounds a person produces can be adjusted to conform to the sounds intended by that person.

Because of age changes in these areas, the voice becomes more variable in pitch and volume during speaking. Female voices often become lower in pitch, while male voices often become higher in pitch. Other common changes include increases in hoarseness, roughness, and extraneous sounds while speaking. The voice often becomes weaker, and elders have declining abilities to speak very quietly or with very loud volume. The ability to control volume declines, and the precision of word pronunciation diminishes.

Language fluency and vocabulary usually do not decline, and often increase. However, phrases and sentences often become shorter, syllables and words are repeated more often, and more words are pronounced incompletely. These trends in speaking become more prominent in stressful situations. Of course, variability among elders increases with age, and some elders retaining the voice and speech of a young adult.

All these changes reduce the effectiveness of vocalization in providing communication. Additionally, some of the pleasure derived from the human voice may be lost. As a result, the contribution of the voice to happy and healthy survival diminishes. Age changes in the voice also alter the way people respond socially to individuals who are getting older. These changes in turn affect aging individuals' responses and self‑images. Therefore, biological aging of vocalization can influence nonbiological aspects of life.