Final answer:
Tension on the true vocal cords controls the pitch of sounds, while volume is affected by the airflow from the lungs. Changes in pitch are achieved by relaxing or tightening the muscles of the larynx, which adjusts the tension on the cords.
Step-by-step explanation:
The tension on the true vocal cords plays a crucial role in controlling the pitch of the sounds produced by our voice. The vocal cords, which are elastic folds in the throat, open and close rhythmically as air travels up from the lungs, creating pressure buildup that results in vibration. When we want to change the pitch of our voice, the muscles surrounding the larynx either relax or tighten, altering the tension on the vocal cords.
Volume, on the other hand, is affected by the flow of air from the lungs. A stronger airflow increases the amplitude of the sound pressure wave, thus making the sound louder. Consequently, control over both the tension of the vocal cords and the air flow from the lungs allows us to adjust the pitch and volume of our voice, respectively.