The more bends the sound waves have to maneuver, the more momentum they loose. Polyurethane foams. Acoustic foams were first used in the mid 's. 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.
Air passes easily, through this type foam. Polyurethane is designed as a flexible, open-cell, porous solid. Sound energy is propagated through the material by two major methods: Sound pressure waves move through the fluid within the pores of the polyurethane Elastic stress waves are created as a result of the pressure waves, which are carried through the frame of the polyurethane Polyurethane is quite effective at attenuating high frequency sound waves, but it does not provide low frequency isolation unless sufficient thickness is used.
Felt is produced by pressing and matting fibers together. Fibres use may be natural mostly wool or synthetic. A blend of both is also common. Felt is durable and stable in the presence of moisture, lubricating oils, greases, salts, detergents, and is inert to many other chemicals. Its ability to bend to uneven surfaces prevents the unwanted intrusion of foreign substances beneath the load-bearing area.
Felt possesses almost permanent resilience, as it is made up of millions of individual fibers. The performance of felt in sound absorbtion is as a result of its optimum density and spring. The absorption of sound waves is achieved by the vibration of individual fibres within the felt. The energy is dissipated by frictional heat loss. Due to its method of absorbtion, too dense felt would not allow for sufficient vibrations. These qualities make it excellent for industrial sound proofing.
Felt is also used as a damper in musical instruments. Polyester fibre. Polyester fibre is a man made fiber, made up of long chain synthetic polymers. They are generally known as non woven or bonded fibre fabric. They are used to make non toxic, light weight insulation products. It's sound absorbtion increases with the frequency of the sound, hence it's most effective at high frequencies. It's NRC rating is between 0.
Polyester fibre is also strong with high tensile strength. Other desirable properties are it's resistance to abrasion, fire, wrinkles, stretch, impact and wear. These properties make it an excellent soundproofing material in industrial and heavy machinery settings. Fiber Glass. Acoustic fiberglass has the desirable combination of rigidity and being light weight. Popularly dubbed, the shape shifter of sound proofing, this material can be very easily customized, to allow for installation in the tightest of places.
Glass fibre is mostly used in rooms and halls to prevent reverberations and echos. Mass Loaded Vinyl has been applied in soundproofing since the s.
It is basically a viscoelastic material, such as polyvinylchloride, that is infused with an inert material, like calcium carbonate or barium sulfate. Viscoelastic materials exhibit both viscous and elastic properties. They will flow, but when the force is removed or reversed, they will go back to their original shape. This attribute, known as hysteresis , contributes to the ability of MLV to attenuate sound.
MLV basically acts like a tuned mass damper, capable of reducing the frequency of waves. When vinyl is exposed to low temperatures, it becomes very hard, but when it is exposed to high temperatures it becomes very compliant. When the elastic component becomes very stiff, the vibration modes of the sheet are tuned to a higher frequency, affecting its ability to attenuate sound at lower frequencies.
As is the other way round, as the temperature increases, the MLV becomes limp, to the point where it doesn't possess enough compliance to vibrate. Plasticizers can be used to ensure the proper compliance of the MLV over the operating temperature range.
Soundproofing Techniques A range of soundproofing techniques can be used to reduce sound within a room: Sound Absorption Porous or resonant absorbing materials can be installed to convert sound wave energy into a tiny amount of heat effectively reducing the amount of sound that is reflected around a room.
Sound Diffusion Irregular surfaces can be used to break down, or scatter sound waves so that they travel along many smaller paths. Sound Reflection Reflecting sound waves is a common technique for reducing traffic noise on freeways and other major traffic routes. Soundproofing Categories Soundproofing falls into two main categories: Reducing sound within a room Soundproofed rooms, also known as anechoic echo free or semi-anechoic chambers, are designed to reduce unwanted reverberation and echo within a room for the purposes of sound-quality e.
Limiting sound leakage Soundproofing materials can be utilised to limit the transference of sound waves between rooms either adjacent, above or below and from external sources.
Soundproofing is the term used for any insulative material used for the purpose of isolating sound. This can take the form of specialised wall coverings and layers of acoustic matting being slotted between a home's framing elements, to simple considerations like thicker underlay beneath the carpet or some weather stripping around doors. Soundproofing is used specifically to control and isolate sound, usually from an unwanted source like a noisy highway or nearby industrial machinery.
Acoustic treatments are commonly applied to home theatres and listening rooms - areas where the direction and flow of sound is considered to be very important. The importance of soundproofing in your housing design cannot be underestimated; the earlier on you plan for this, the easier it is to achieve effectively.
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