Final answer:
Stiffness is not a component that influences impedance. Impedance is affected by the frequency of the transducer, density of the medium, and propagation speed of the wave.
Step-by-step explanation:
The component that does not influence impedance is 'stiffness.' Impedance in the context of waves is affected by a variety of factors, including the frequency of the transducer, density of the medium, and the propagation speed of the wave. The frequency of a wave is dependent on the propagation speed and the length of the string, as well as on the density and the stiffness of the medium. The speed of sound or any mechanical wave depends on the properties of the material through which it travels. When considering the relationship between frequency, wave speed, and density, we understand that waves propagate faster in a less dense medium if the stiffness is the same. None of the options provided, which are frequency, density, and propagation speed, are unrelated to impedance, as they all play a role in wave behavior.