Periodic waves can be characterized as:

Periodic waves are characterized by the property of having a consistent and repeating pattern over time. This means that the wave form is predictable, allowing us to identify specific cycles within the wave. The concept of periodicity is fundamental in wave mechanics and is evident in various types of waves, including sound waves.

When discussing periodic waves, we often find that they generate tones that are perceived as musical or harmonic because of their predictable structure. This pattern is crucial in fields such as acoustics and speech science, where understanding the characteristics of sound waves aids in analyzing speech and other audio phenomena.

The other options do not accurately describe periodic waves. For example, waves characterized by having no noticeable pattern would be considered aperiodic, which is the opposite of periodic waves. Additionally, while certain sounds (such as vowels) may generate periodic waves, this property is not exclusive to them; other speech sounds and musical notes can also be periodic. Distortion is related to variations in wave forms caused by factors such as interference or non-linear effects and does not define periodic waves themselves. Thus, the defining characteristic of periodic waves lies in their self-repeating nature with a noticeable and predictable pattern, making option B the correct choice.