Respiratory and laryngeal measures of children during vocal intensity variation.

Simultaneous aerodynamic, acoustic, and kinematic measurements from the laryngeal and respiratory systems were made in order to study mechanisms for changing vocal intensity. Aerodynamic and acoustic measures include an approximation of open quotient, maximum flow declination rate, alternating glottal airflow, estimated tracheal pressure, sound pressure level, and fundamental frequency. Respiratory measures included lung volume, rib cage, and abdominal displacements. Adults were used as a comparison group to twenty 4-year-olds and twenty 8-year-olds. Laryngeal and respiratory results indicate that speech production differences between the children and adults are based both on size and function. For example, children's absolute anteroposterior diameters of the rib cage are smaller than adults, but their rib cage movement is larger and encompasses a different range during speech breathing. Since children are functionally different than adults, age specific speech production models need to be developed.