波的产生:
在弹性介质中，任何一个质点作机械运动时，因为这个质点与邻近的质点间有相互作用的弹性力联系着，所以它的振动将传递给与之相邻近的质点，使邻近质点也同样地发生振动，然后又传给下一个质点，依此类推。这样，振动就由近及远地向各个方向以一定速度传播出去，从而形成了机械波。波动只是振动在介质中的传播过程。在波动过程中，介质中的各点只是在自己的平衡位置附近振动而并没有随波前进。机械波的产生，首先要有作机械运动的波（声）源，其次要有传播这种机械波的介质。（Wave generation:
In elastic media the mechanical movement of any one dot because the dots and adjacent dots between the interaction of the elastic force of contact ａnd therefore its vibration will be passed to the associated adjacent dot the adjacent dot also occur vibrations and then passed to the next dot ａnd so on. Vibration from near ａnd far to a certain speed in all directions spread out to form a mechanical wave. Fluctuations just vibration propagation medium. In the fluctuations in the process the various points in the medium only in the vicinity of the equilibrium position of vibration and not with wave forward. Mechanical wave generation first of all have to make the mechanical motion of the waves （sound） source followed have spread this mechanical wave medium.）
波的种类:
波有不同的种类，这是根据介质质点的振动方向和波的传播方向的关系来区分的。
（1）纵波 介质质点的振动方向与波的传播方向一致，这种波称为纵波，纵波又称“P”波。
纵波是靠介质的压缩与膨胀变形来传递力使波传播。固体、液体、气体在被压缩或膨胀时都可以产生应力，所以固体、液体、气体都能传播纵波。空气、水中传播的声音就是纵波。纵波可以在固体、液体、气体中传播。
（2）横波 介质质点的振动方向与波的传播方向垂直，这种波称为横波，横波又称“S”波。
横波是靠介质的剪切变形来传递力使波传播。图1中沿绳子传播的波属于横波。液体、气体在被剪切时并不产生应力，所以液体、气体不能传播横波。液体、气体中只有纵波存在。横波只能在固体中传播。
（3）表面波有一种波专门沿表面传播，称为表面波，表面波又称“R”波。表面波也只能在固体中传播。
（Type of wave:
The wave has a different species which is
（1） of the vibration direction of the longitudinal wave medium dot is consistent with the direction of propagation of the wave this wave is called the longitudinal wave the longitudinal wave also known as the "P" wave.
Longitudinal wave is to rely on media compression and expansion deformation to transmit force to the wave propagation. The solids liquids gases can be compressed or expanded when stress is generated so as solids liquids gases can spread to the longitudinal wave. Air the propagation of sound in water is the longitudinal wave. The longitudinal waves can be propagated in the solid liquid and gas.
（2） shear wave dielectric particle vibration direction perpendicular to the direction of propagation of the wave this wave is called a shear wave shear wave also known as "S" wave.
Shear wave is transmitted by the shear deformation of the medium to the force of the wave propagation. Figure 1 the wave propagation along the rope is a transverse wave. Liquid gas does not generate the shear stress ａnd therefore liquids gases can not propagate shear waves. Liquids gases only longitudinal waves exist. The transverse waves in solids only spread.
（3） The surface acoustic wave has a wave specifically along the surface propagation known as the surface acoustic wave SAW also known as the "R" wave. SAW can only spread in solids.）
声波的衰减:一个声音在传播过程中将越来越微弱，这就是声波的衰减。造成声波衰减的原因有以下三个:扩散衰减:物体振动发出的声波向四周传播，声波能量逐渐扩散开来。能量的扩散使得单位面积上所存在的能量减小，听到的声音就变得微弱。（超声波探伤仪）单位面积上的声波能量随着声源距离的平方而递减。（Acoustic attenuation: a voice in the communication process will become increasingly weak and this is the acoustic attenuation. Three reasons: diffusion attenuation of sound attenuation: the
吸收衰减:声波在固体介质中传播时，由于介质的粘滞性而造成质点之间的内摩擦，从而使一部分声能转变为热能;同时，由于介质的热传导，介质的稠密和稀疏部分之间进行热交换，从而导致声能的损耗，这就是介质的吸收现象。介质的这种衰减称为吸收衰减。通常认为，吸收衰减与声波频率的一次方、频率的平方成正比。（Absorption attenuation: the propagation of acoustic waves in a solid medium due to the viscosity of the medium is caused by internal friction between the dots so that the part of the sound energy into heat energy; the same time since the thermal conductivity of the medium the medium between the dense and sparse portionsfor heat exchange resulting in the loss of acoustic energy and this is the phenomenon of the absorption of the medium. This attenuation is referred to as medium absorption ａnd attenuation. Generally accepted that the first absorption ａnd attenuation of acoustic frequency is proportional to the square of the frequency.）
散射衰减:当介质中存在颗粒状结构（如液体中的悬浮粒子、气泡，固体中的颗粒状结构、缺陷、搀杂物等）而导致的声波的衰减称散射衰减。通常认为当颗粒的尺寸远小于波长时，散射衰减与频率的四次方成正比;当颗粒尺寸与波长相近时，散射衰减与频率的平方成正比。扩散衰减只与距声源的距离有关，与介质本身的性质无关。吸收衰减与散射衰减大小则取决于声波的频率和介质本身的性质。（超声波探伤仪）（The scattering attenuation: the attenuation when the granular structure is present in the medium （such as the suspended particulates in the liquid bubbles solid particulate structure defects dopant etc.） resulting from the attenuation of sound waves said scattering. Usually considered when the particle size is much smaller than the wavelength the scattering attenuation with frequency proportional to the fourth; scattering attenuation with frequency proportional to the square when similar particle size and wavelength. The diffusion attenuation is only related to the distance from the sound source and regardless of the nature of the media itself. Absorption attenuation and scattering attenuation size depends on the frequency of sound waves and the nature of the medium itself.）
来源：阿仪网(www.app17.com) http://www.app17.com/c72093/article/d151738.html#
