Acoustic impedance
Acoustic impedance Z (Characteristic impedance or sound impedance) is the ratio of sound pressure p to sound velocity (particle velocity) v, which is constant at every point of a room and is dependent on the temperature. See table: acoustic impedance vs. temperature.
Also it is the product of the density of air ρ (rho) 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 = degree Celsius and °F = degree Fahrenheit.
p = sound pressure in N/m2 = Pa = pascal
v = sound velocity (particle velocity) in m/s
J = sound intensity in W/m2
F = force in N = newton
ρ (rho) = density of air in kg/m3
c = acoustic impedance, sound impedance, or characteristic impedance in N·s/m3
Table - Acoustic impedance Z, Speed of sound in air c,
density of air ρ vs. temperature °C
| Impact of temperature | |||
| °C | c in m/s | ρ in kg/m³ | Z in N·s/m³ |
| - 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 |
External link
- Ohm's law of the acoustics - calculation of acoustic impedance Z sound pressure p particle velocity v sound intensity J (http://www.sengpielaudio.com/calculator-ak-ohm.htm)
de:Schallkennimpedanz
Categories: Acoustics