Sound insulation and absorption are two completely different concepts,and sound insulation materials have a high density and density;The sound-absorbing material has a low density and is loose.The main performance of sound insulation materials is sound insulation,with low sound absorption rate;The main performance of sound-absorbing materials is sound absorption,while the sound insulation is small.
　　Sound insulation is one of the important means of noise control,which limits noise to a certain spatial range,prevents external noise from entering,or isolates strong noise in a specific range,thereby providing people with a suitable environment.
　　The structural characteristic of porous sound-absorbing materials is that they have a large number of interconnected pores and bubbles inside and outside.When sound waves enter them,they can cause air vibration in the pores.Due to the viscous resistance of the air and the friction between the air and the hole wall,a considerable amount of sound energy is converted into heat energy and lost.In addition,when air is adiabatic compressed,heat exchange occurs continuously between the air and the hole wall.Due to thermal conduction,a portion of sound energy is also converted into heat energy and absorbed.If the micropores of porous materials are sealed by dust,dirt,or paint,it will have an adverse effect on the sound absorption performance of the material.
　　If a wall is made of sound-absorbing material with a sound absorption coefficient of 0.99(equivalent to a pointed structure),and the remaining 0.01 sound energy can pass through this wall,its sound insulation is only 20dB.However,achieving a sound absorption coefficient of 0.99 for an sound-absorbing structure is quite difficult and costly.It is easy to obtain a sound insulation of 20dB using dense materials,which indicates that sound insulation and absorption are two completely different concepts and cannot be confused.