The _____ is the acoustic resistance to sound traveling in a medium.

• A. Density
• B. Impedance
• C. Velocity
• D. Absorption

Answer: (B)

Acoustic impedance captures how much a medium resists the motion of particles as a sound wave travels through it. It’s defined as the ratio of acoustic pressure to particle velocity, Z = p/v, and for plane waves in a uniform medium it can be written as Z = ρc, where ρ is density and c is the speed of sound. This combination specifically measures the opposition to motion that the medium offers to the wave, which in turn governs how much of the wave is transmitted versus reflected at boundaries. That’s why impedance is the right term for acoustic resistance to traveling sound. Density alone describes how much matter is present, velocity describes how fast the wave moves, and absorption describes energy loss, not the resistance to propagation itself.