In theory, general objects have sound insulation, but we use the average sound insulation (in an infinite space, an infinite material between the sound source and the measured point) more than 30dB of the board is called the sound insulation board . The baffles are generally high density materials.
Sound is a wavy energy that requires media to spread. When sound is propagating in the same medium, the higher the density of the medium, the faster the propagation speed. For example, the propagation speed in normal air is about 340 m / s, and the propagation speed in the rail is about 5200 m / sec.
Another spread of sound is the spread across media. That is, from one medium, through the critical contact surface of the two mediums into another medium, at this time, the transmission of acoustic energy is essentially the transmission of the vibration amplitude. When transmitting across a medium, the greater the difference in density between the two media, the greater the loss of acoustic energy. In practical applications, air is the active space under human normal, so the material that differs greatly from the air density is generally a material with a high density (a material much lower than the air density, but not much vacuum), ie Can be considered as sound insulation material. The higher the density, the better the sound insulation. A sheet made of such a material is called a baffle.
The soundproof board is not blocked by sounds of all frequencies. The object has a natural resonant frequency, the sound close to the resonance frequency of the object, and the sound insulation effect of the soundproof board is significantly reduced.
The sound insulation board has the difference of air sound and vibration sound. Air acoustic baffles, ie plates that block the sound that travels in the air. Vibrating acoustic baffles are barrier plates and systems that propagate sound in rigid components such as reinforced concrete monolithic houses.
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