Acoustic impedance
Acoustic impedance Z (Characteristic impedance) is the ratio of sound pressure p to sound velocity v, which is constant at every point of a room.
Also it is the product of the density of air ρ and the speed of sound c.
The acoustic impedance Z in N·s/m³ is:
The acoustic impedance (characteristic impedance) of air is Z = 410 N·s/m³ at the temperature 25°C (77°F) or 413 N·s/m³ at 20°C (68°F). C = Centigrade or Celsius and F = Fahrenheit.
p = Sound pressure in N/m² = Pa = Pascal
v = Sound velocity in m/s
J = Sound intensity in W/m²
F = Force in N = Newton
ρ = rho = Density of air in kg/m³
c = Speed of sound in m/s
Z = Acoustic impedance in N·s/m³
| Impact of temperature | |||
| °C | c | ρ | Z |
| - 10 | 325,4 | 1,341 | 436,5 |
| - 5 | 328,5 | 1,316 | 432,4 |
| 0 | 331,5 | 1,293 | 428,3 |
| + 5 | 334,5 | 1,269 | 424,5 |
| + 10 | 337,5 | 1,247 | 420,7 |
| + 15 | 340,5 | 1,225 | 417,0 |
| + 20 | 343,4 | 1,204 | 413,5 |
| + 25 | 346,3 | 1,184 | 410,0 |
| + 30 | 349,2 | 1,164 | 406,6 |