Propagation speed is only determined by:

Propagation speed in ultrasound refers to the speed at which sound waves travel through a medium. The primary factor that determines this propagation speed is the characteristics of the medium itself, specifically its density and stiffness. In general, sound travels faster in solids than in liquids, and faster in liquids than in gases due to differences in molecular composition and bonding.

While frequency can affect other aspects of ultrasound, such as wavelength and penetration depth, it does not influence the speed of sound in the medium. Similarly, temperature can have an impact on the properties of the medium—like speed in gases particularly—but it is not the primary determinant of propagation speed. Pulse duration relates to the length of time a pulse is emitted and does not affect the speed of sound in the medium.

The propagation speed is fundamentally linked to the medium, thereby making the characteristics of the medium the sole determinant in this context.