| Abstrakt: |
The orifice impedance model usually works well for modeling sound transmission through an orifice. However, for a long orifice or for an orifice with a large load impedance, the standard impedance model may be invalid. The goal of this paper is to establish when the orifice impedance model gives a valid estimate of the impedance of a tube in series with a load impedance. The method involved a comparison of the orifice impedance model with a transmission line model. Comparison showed that if both |Γkl|<0.1 and |ZL/Zc| <0.1, then the orifice impedance model is valid (Γ is the propagation coefficient, k is the wave number, l is the tube length, and ZL/Zc is dimensionless load impedance). If either of these limits is unsatisfied, then the validity of the orifice impedance model depends on six variables. Numerical comparisons of the two models showed the effects of these variables. Computations were restricted to air, and most calculations were in the shear wave-number range of 1≤S≤100 [S=r0(ω/ν)1/2, where r0 is tube radius, ω is frequency, and ν is kinematic viscosity]. Graphical results show the limits of validity of the orifice impedance model. [ABSTRACT FROM AUTHOR] |
