Shear waves travel in more than one direction and when they encounter another boundary material they change speed and go in more than one direction again. This repeats until there is no boundary or no motion. Shear in materials is why and how we can tell the difference between brass and lead. Knowing how shear works allows us to design better sounding and more efficient audio products..even the lowly fuse with at least 3 surface boundaries for shear wave resonance to ricochet off. Tom
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