Atoms in all materials are constantly shaking, which is largely responsible for the transfer of heat and sound. In a uniform crystalline solid, the motion of the lattice can be decomposed into just a handful of normal modes of vibration or, in the language of quantum mechanics, a set of quantized eigenmodes of the elastic structure known as phonons [1]. In the frequency (f) regime of interest for microwave engineers, there exist three (one longitudinal, two shear) branches of vibrational modes with long wavelengths-"long" when compared with the atomic spacing. Their frequencies, which represent the energy of each quantum, are linearly proportional to the inverse wavelengths, which represent the momentum of each quantum. The ratio between the two is typically several kilometers per second. In good crystals with few imperfections, these vibrations travel a very long distance-"long" when compared with the wavelength-with little decay of the amplitude under the ambient temperature and pressure. At audio frequencies, these sound waves can propagate in solids. They are commonly known as acoustic waves (see "Nomenclature Used Throughout").

中文翻译：

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通过微波显微镜对声波进行成像：用于可视化千兆赫声波的微波阻抗显微镜

所有材料中的原子都在不断振动，这在很大程度上是热量和声音传递的原因。在均匀的结晶固体中，晶格的运动可以分解为少数正常振动模式，或者用量子力学的语言来说，是一组称为声子的弹性结构的量子化本征模式 [1]。在微波工程师感兴趣的频率 (f) 范围内，与原子间距相比，存在具有长波长的三个（一个纵向，两个剪切）振动模式分支 - “长”。它们的频率代表每个量子的能量，与代表每个量子动量的反波长成线性比例。两者之间的比率通常为每秒几公里。在几乎没有瑕疵的好晶体中，这些振动传播的距离非常长——与波长相比“长”——在环境温度和压力下振幅几乎没有衰减。在音频频率下，这些声波可以在固体中传播。它们通常被称为声波（参见“自始至终使用的命名法”）。