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BIO Waves on vocal cords. In the larynx, sound is produced by the vibration of the vocal cords. The diagram in Figure 12.44 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 cords. In a typical adult male, the thickness of the vocal cords 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 cords travels upward at a speed of u = 375 cm/s. Take t to be time, z to be displacement in the + z direction, and λ to be wavelength.
Figure 12.44 Problems 72–74.
74. The wave speed is measured for different vibration frequencies. A graph of the wave speed as a function of frequency (Fig. 12.45) indicates that as the frequency increases, the wavelength
- A. increases.
- B. decreases.
- C. doesn’t change.
- D. becomes undefined.
Figure 12.45 Problem 74.
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