ARDMS Ultrasound Physics & Instrumentation Practice Exam

In the context of ultrasound physics, the propagation speed of sound in a medium is influenced by both the density of the medium and its elasticity. The propagation speed can be described by the formula: \[ c = \sqrt{\frac{E}{\rho}} \] where \( c \) is the speed of sound, \( E \) represents the elasticity (or bulk modulus) of the medium, and \( \rho \) is the density. When only the density of the medium is increased, assuming that the elasticity stays constant, the formula indicates that the speed of sound will decrease. This is because increasing density (\(\rho\)) while keeping elasticity (\(E\)) the same results in a larger denominator in the fraction that determines propagation speed. As density increases, the speed of sound is inversely affected, leading to a decrease in propagation speed. Thus, it is accurate to state that when only the density of a medium is increased and elasticity does not change, the propagation speed will decrease.