Elastic stress waves are created as a result of the pressure waves, which are carried through the frame of the polyurethane.Sound pressure waves move through the fluid within the pores of the polyurethane.Sound energy is propagated through the material by two major methods: Polyurethane is designed as a flexible, open-cell, porous solid. Air passes easily, through this type foam. Polyurethane foams are made through basic addition polymerization reaction involving a diol or polyol, a diisocyanate, and water.Acoustic foams have mostly open cells as a result of trapped gas bubbles which pop. Acoustic foams were first used in the mid 1970's. let us now take a look at some unique, soundproofing materials. The above properties qualify a material as good for soundproofing. The more bends the sound waves have to maneuver, the more momentum they loose. This is a measure of the twists and turns in the material's cell arrangement. Open cell arrangement make better absorbers, while closed cell arrangements make better blockers. The cell size of the material must be smaller than the wave length of the sound it is meant to absorb or block. The individual cells of the material, have to be adequately small for the material to qualify for soundproofing. Resistivity is dependent on tapers of the sound waves. It is the most important characteristic of sound absorbers. This is the flow resistance to noise per unit thickness of a material. Porosity is an advantage in absorption and a disadvantage in blocking. This property involves the use of intersiticies to alter the energy of the sound waves by expansion, compression and change in the direction of flow resulting in loss of momentum. If the density is too high, the waves get reflected off the material's surface. If the material's density is too low, the sound waves are transmitted through. High enough and sound waves get damped low enough and they get absorbed. For a material to be sound proof it has to fall within a proper density range. It is measure of how packed together, the molecules of a material are. Density is the amount of mass per volume of a substance. Before studying some of these materials, we need to first get an understanding of what properties make these materials unique. There are a few materials that can effectively carry out soundproofing. One might imagine that soundproofing can be achieved by any material, this is however, far from the case. Damping: A form of absorption in which the oscillating sound waves are made to undergo resonance, with respect to the surface it hits.The sound energy is converted to kinetic energy through vibrations, and finally to a miniscule amount of heat, through inter molecular friction. When sound waves hit any surface, some get transmitted through the material, some get absorbed within the material and a percentage gets reflected (depending on the absorbing quality of the surface). In absorption, soundproofing is achieved by the reduction of the energy of the sound waves. Absorption: Absorption and/or damping are complex forms of soundproofing, through the use of materials.As a result, the longer the distance the waves have to travel to reach the receptor, the more of its energy is lost. Distance: When traveling through a medium e.g air, the sound energy of the waves is gradually lost converted to vibrational (kinetic) energy in the atoms of the medium.The act of eliminating, reducing or blocking sound is referred to as sound proofing, which can be done in the following three basic ways: Although they cannot be completely blocked, they can be greatly reduced. Since they are waves, sound energy can refract, reflect and maneuver around edges. The noise of a motor engine, external noise in a music studio, noise from a shared apartment etc.There is therefore need for a means or technique to reduce or block it. It's this energy that enables the sound waves to be propagated.ĭespite its vast applications and usefulness, this form of energy is sometimes unwanted and becomes a nuisance or hinderance. These vibrations are converted from kinetic energy to sound energy. Sound waves are as a result of vibrations between atoms or molecules. As energy, it can be used to break down solids and degas liquids. Aside from being a major form of communication, it's also put to task in geophysics in aspects of signalling, location and positioning. Sound is undeniably a very important aspect of our existence.
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