[求助]什么是声阻率？ - 微型电声器件设计室 - 声学楼论坛

The acoustic impedance Z (or sound impedance) is a frequency f dependent parameter and is very useful, for example, for describing the behaviour of musical wind instruments. Mathematically, it is the sound pressure p divided by the particle velocity v and the surface area S, through which an acoustic wave of frequency f propagates. If the impedance is calculated for a range of excitation frequencies the result is an impedance curve. Plane, single-frequency traveling waves have acoustic impedance equal to the characteristic impedance divided by the surface area, where the characteristic impedance is the product of longitudinal wave velocity and density of the medium . Acoustic impedance can be expressed in either its constituent units (pressure per velocity per area) .

$Z = \frac{p}{vS} \,$

Note that sometimes vS is referred to as the volume velocity.

The specific acoustic impedance z is the ratio of sound pressure p to particle velocity v at a single frequency. Therefore

$z = \frac{p}{v} = ZS=$

Distinction has to be made between:

the characteristic acoustic impedance $Z 0$ of a medium, usually air (compare with characteristic impedance in transmission lines).
the impedance $Z$ of an acoustic component, like a wave conductor, a resonance chamber, a muffler or an organ pipe.

A rayl is one of two units of acoustic impedance. When sound waves pass through any physical substance the pressure of the waves causes the particles of the substance to move. The sound impedance is the ratio between the sound pressure and the particle velocity it produces. The impedance is one rayl if unit pressure produces unit velocity.

The units are named for John William Strutt, 3rd Baron Rayleigh (12 November 1842 – 30 June 1919). They have the same name when using either the CGS definition or the MKS-based definition, but not the same value:

In MKS units, 1 rayl equals 1 pascal-second per meter (Pa·s·m^?1), or equivalently 1 newton-second per cubic meter (N·s·m^?3). In SI base units, that’s kg?s^?1?m^?2.
In CGS units, 1 rayl equals 1 dyne-second per cubic centimeter (dyn·s·cm^?3).

1 CGS rayl = 10 MKS rayls.

声阻抗

由于吸声系数主要反映入射声和反射声能量的数值关系，它们的位相关系并没有反映出来，在这方面声阻抗可能更有价值。介质在某一表面上的声阻抗由该介质表面上的平均有效声压和通过该表面上的有效体积速度的比值来表示：声阻抗是一个复数，其实部为声阻，虚部为声抗。介质中某一点的有效声压和该点的有效质点速度的比值称为声阻抗率：吸声材料的声阻抗和吸声系数一样，可以利用驻波管进行测量，直接由测量结果画出材料的声阻抗图。

流阻、空隙率是表征多孔性吸声材料的主要微观物理参数，它可以帮助从材料的微观结构入手，改进多孔性吸声材料的吸声特性。流阻表征气流通过材料的阻力，也是俗称的材料的透气性。

从根本上讲，材料的流阻和声阻有密切关系。一般说来对于低流阻材料，低频范围的吸声系数较低，中高频范围明显增加;高流阻材料相比较在高频范围吸声系数较低，而低频范围有一定改善。

材料学是比较复杂,在电声器件中,从等效电路原理出发,声阻抗是比较有用的基本概念之一!

主题：[求助]什么是声阻率？