Metal foam is mainly used in the automotive industry for impact buffering of the car body and noise reduction and heat insulation of the car body and partition walls. 
Through-hole metal foam is a specially processed high-permeability porous material, which has a sponge-like porous structure from the inside to the outside. The entry of sound from the surface into its interior causes the small fibers of air and material in the pores to vibrate, and through friction and viscous resistance, the sound energy is converted into heat energy and absorbed. 
Compared with other sound-absorbing materials, foamed metal materials have high sound-absorbing characteristics in the low-frequency range. According to the choice of the thickness of the air layer, it shows excellent sound-absorbing effect when it involves a wide range of low-frequency fields. 
It is used for sound absorption of high-speed rail car boxes, not only has good sound absorption performance, but also has better anti-deformation performance than traditional polyester materials, has good energy absorption performance, high strength, non-combustion, and increases the safety of transportation equipment; at the same time Metal materials are non-toxic and harmless, and are more in line with environmental protection standards.