Which term describes the measure of how much sound is reflected versus transmitted at a boundary?

The term that describes the measure of how much sound is reflected versus transmitted at a boundary is the reflection coefficient. This coefficient quantifies the fraction of the incident sound wave's intensity that reflects off an interface, like the boundary between different tissues in ultrasound imaging. It is calculated based on the acoustic impedances of the two materials at the boundary.

Understanding the concept of the reflection coefficient is crucial in ultrasound as it directly impacts the image quality and diagnostic information obtained. A high reflection coefficient indicates that a significant portion of the sound wave is reflected, which can enhance the visibility of structures but may also lead to reduced transmission into deeper tissues. Conversely, a lower reflection coefficient suggests that more of the sound wave is transmitted, potentially allowing for deeper tissue evaluation.

The other terms, while related to sound and its behavior, describe different phenomena. Gain refers to the amplification of the received ultrasound signals, while the transmission coefficient describes the fraction of sound intensity that is transmitted through the boundary. Impedance refers to the resistance encountered by sound waves as they travel through a medium, which is relevant for understanding reflection and transmission but does not directly measure the reflection versus transmission ratio itself.