Acoustic Impedance
- The total reaction of a medium to the transmission of sound through it, expressed as the ratio of sound pressure to particle velocity at a given point in the medium. The acoustic impedance Z is useful in describing the acoustic radiation from sources such as surfaces and ducts.
- where
- Z = acoustic impedance [rayls or kgm-2s-1]
- p = acoustic pressure [Pa]
- U = particle velocity [ms-1]
- p = acoustic pressure [Pa]
- The acoustic impedance of air is the density ρ times the speed of sound c
- Also known as characteristic impedance.
- The acoustic impedance of a duct is
- where
- S = cross-sectional area of the duct [m2]
- For a typical air intake duct of internal radius 0.03m the impedance Z0=1.47x106.
See also: Acoustic Admittance, Acoustic Ohm, Acoustic Reactance, Acoustic Resistance, Duct Acoustics, Impedance, Rayl.
Subjects: Noise & Vibration