Final answer:
The statement that is not true of vibrations is that they always result in the production of sound. Not all vibrations result in audible sound, as it depends on factors such as frequency and energy.
Step-by-step explanation:
The accurate answer to the question "Which of the following statements is not true of vibrations?" is c) Vibrations always result in the production of sound. While vibrations are indeed the source of sound waves when an object vibrates within the audible frequency for humans, not all vibrations produce sound that humans can perceive. For instance, vibrations might occur at frequencies outside the audible range or may not have enough energy to create an audible sound. Therefore, statement c is not always true.
Vibrations are typically associated with periodic back-and-forth motions and can indeed be characterized by frequency and amplitude. Additionally, vibrations can travel through various mediums, such as air, water, and solids, which facilitates the propagation of mechanical waves like sound waves. However, certain types of waves, like electromagnetic waves (light for example), do not require a medium to travel and can even move through a vacuum, which is not the case with mechanical waves like sound.