Question

Describe the difference between acoustic impedance, specific acoustic impedance and characteristic acoustic impedance.

Answer 1

Acoustic Impedance ) At the given surface, the complex ratio of effective sound pressure averaged over the surface to the effective flux (volume velocity or particle velocity multiplied by the surface area) through it. The unit is N-s/m⁵.

Specific Acoustic Impedance ) Specific Acoustic Impedance is the complex ratio of the effective sound pressure at a point to the effective particle velocity at a point. The unit is N-s/m³.

Characteristic Acoustic Impedance ) The absolute value of the acoustic impedance is often called characteristic acoustic impedance and denoted Z₀ .

Z₀ = pc/A

p is volumetric mass density of the medium.

c is speed of sound waves traveling in the medium.

A is aperture with area A

Z₀ is characteristic acoustic impedance.