The wave speed is measured for different vibration frequencies. A graph of the wave speed as a function of frequency (Fig. P15.80) indicates that as the frequency increases, the wavelength

(a) Increases;

(b) Decreases;

(c) Doesn€™t change;

(d) Becomes undefined.

Figure P15.80

In the larynx, sound is produced by the vibration of the vocal folds (also called €œvocal cords€). The accompanying figure is a cross section of the vocal tract at one instant in time. Air flows upward (in the +z direction) through the vocal tract, causing a transverse wave to propagate vertically upward along the surface of the vocal folds. In a typical adult male, the thickness of the vocal folds in the direction of airflow is d = 2.0 mm. High speed photography shows that for a frequency of vibration of f = 125 Hz, the wave along the surface of the vocal folds travels upward at a speed of v = 375 cm/s. Use t for time, z for displacement in the +z-direction, and l for wavelength.

Transcribed Image Text:

v (cm/s) 1200 1000 800 600 400 200 f(Hz) 50 100 150 200 250 300 350 400 Vocal fold Airflow