Propagation & Impedance - Video Lesson

Welcome back to our series on sound and sound waves in ultrasound imaging. This lesson looks at propagation and impedance, how to calculate acoustic impedance, analyze its effects on imaging, and predict potential artifacts that can appear during a scan. Understanding these underlying properties of sounds and how they interact with tissues in the body is essential to producing quality diagnostic sonograms. Let's start by discussing the concept of propagation. As you might remember, sound waves travel by pushing particles together in moments of compression and through moments of rarefaction where the particles separate themselves again. Without a medium to travel through, there are no particles to push into one another, so sound waves are not able to propagate. Propagation speed then is the measure of how fast sound waves travel through a medium. In most soft tissues, the speed is about fifteen hundred and forty meters per second. This number was arrived at by taking an average of