Impedance increases when density and propagation speed increase. It is affected by stiffness and is not affected by which property?

Impedance increases when density and propagation speed increase. It is affected by stiffness and is not affected by which property?

• A. Density and Temperature, and it is affected by Temperature, and not affected by Speed.
• B. Propagation speed alone, and it is affected by Density, and not affected by Frequency.
• C. Density and Propagation speed, and it is affected by Stiffness, and not affected by Frequency.
• D. Density alone, and it is affected by Temperature, and not affected by Propagation speed.

Answer: (C)

Impedance in a uniform medium is the product of density and wave speed. When density goes up or when the propagation speed goes up, impedance increases. The propagation speed itself is influenced by stiffness: in solids, stiffer materials let waves travel faster, so increasing stiffness raises the speed and thus increases impedance (assuming density stays the same). In this simple model, impedance does not depend on frequency, so frequency doesn’t change impedance. That’s why the statement that matches is: impedance depends on density and propagation speed, is affected by stiffness, and is not affected by frequency. The other options either imply a dependence on frequency or omit one of the essential factors (density or speed), which doesn’t fit the relationship Z = ρc.

Impedance in a uniform medium is the product of density and wave speed. When density goes up or when the propagation speed goes up, impedance increases. The propagation speed itself is influenced by stiffness: in solids, stiffer materials let waves travel faster, so increasing stiffness raises the speed and thus increases impedance (assuming density stays the same).

In this simple model, impedance does not depend on frequency, so frequency doesn’t change impedance. That’s why the statement that matches is: impedance depends on density and propagation speed, is affected by stiffness, and is not affected by frequency. The other options either imply a dependence on frequency or omit one of the essential factors (density or speed), which doesn’t fit the relationship Z = ρc.