各向同性材料
某一材料性能在各个方向上都相同的材料——即材料性能与测试方向无关。只需两个弹性常数（即弹性模量、剪切模量或泊松比中的任意组合）即可完整表征各向同性材料。其 实际意义在于：对于各向同性材料，波速在各方向上相同。因此，对于给定的变幅杆设计和指定频率，变幅杆的调谐长度不会因其从原材料的哪个方向加工而改变。
铝接近于各向同性。
Isotropic material
A material for which a given material property is the same in every direction - i.e., the material properties do not depend on the direction in which the material is tested. Only two elastic constants (i.e., any combination of modulus of elasticity, shear modulus, or Poisson's ratio) are needed to fully characterize an isotropic material. The practical consequence is that, for an isotropic material, the wave speed is the same in every direction. Thus, for a given horn design and specified frequency, the horn's tuned length will not depend on which direction the horn was machined from the original material.
Aluminum is nearly isotropic.
Also see —
Anisotropic
Homogeneous
Orthotropic