What term describes the rate at which sound waves pass through various substances in ultrasonics?

The concept of "velocity" in ultrasonics refers to the speed at which sound waves travel through different materials. This is a critical factor in ultrasonic testing as it affects the propagation of the sound waves and consequently the results gathered from the inspection.

The velocity of sound varies depending on the material through which it is traveling; for instance, sound travels faster in solids than in liquids and faster in liquids than in gases. Understanding this relationship enables technicians to make accurate measurements and interpretations of the data collected when evaluating the integrity of materials.

Other terms like pitch, frequency, and intensity, while related to sound, do not specifically denote the rate of sound wave propagation. Pitch pertains to the perceived frequency of a sound and its relation to how high or low it sounds to the listener. Frequency refers to the number of cycles of a sound wave that occur in a second, measured in Hertz. Intensity deals with the power of the sound wave per unit area. While these aspects are important in the study of sound, they do not define the speed of sound waves in materials, which makes velocity the correct answer in this context.