Acoustics and Sound Insulation Methods

acousticals and effectual Insulation MethodsAcoustics and blend in InsulationABSTRACTAcoustics is the bailiwick of vowelize. The knowledge of this field is necessary as it helps in creating peaceful surroundings. The technical knowhow of healthful insulation has been helpful in constructing functional theatres, infirmarys, Auditoriums, jam pads, and so on hearty is created when a surface vibrates. When this vibration is periodic or rhythmic then the large(p) produced is pleasing to the ears eg. Musical Notes. On the contrary when the vibration is non-periodic and irregular then it is termed as noise. eg. Infants crying.INTRODUCTIONSound travels in the form of longitudinal waves. Each wave moves backward and forward passing on the vibration to the next. For us to be able to hear sizable clearly it is very important for the waves to travel uninterrupted. It is proven that sound travels the fastest in solids, then in liquids and the least in air. This is because in solid the m olecules be so tightly packed that the transmission is the easiest. In liquids too the molecules be fairly close to each other where as in air it becomes a little tough for sound to travel. Sound throw outnot travel in vacuum as it needs a medium to travel. The induce of sound in air depends upon the moisture or dryness in air. The much the moisture the faster sound will travel.CHARACTERISTICS OF SOUNDIntensity and meretriciousness of soundLoudness is the response of humans to the impact of sound. Whereas intensity is the amount of sound waves passing done per unit athletic field per unit time.Frequency and instalSounds dismiss be of diametric types and wavelengths. Pitch isWhat helps us distinguish between sounds of same loudness but of different frequencies. This is thecharacteristic which helps us recognise a mans voice andwomens Voice.QualityThe quality of sound is what enables us to differentiate between deuce musical tones played on different instruments. A study ha s shown that the notes produced by instruments are at times pure notes. They have some fundamental tones of frequency fo and additional tones of frequency 2fo, 4fo, etc. called over tones. The fundamental is heard very clearly because it has expectanter impact human ear.TABLE 1.1, ACCEPTABLE interference LEVELTYPE OF BUILDINGNOISE LEVEL RANGE ( decibels, db)1. Radio and T.V. studio25-302. Music Room30-353. Hospitals and auditoriums35-404. Apartments, hotels and homes35-405. Conference entourage and libraries35-406. Class rooms40-457. Banks and stores45-508. Restaurants50-552REFLECTION OF SOUNDSound waves from a plain surface reflect in the same way as that of light. The angel of incidence is equal to the angel of reflection.Following are the characteristics of reflection of soundWhen sound waves reflect from a flat surface the wave fronts form a spherical shape and the centre of curvature is the source of soundWhen sound waves reflect from a convex surface they get magnified and t herefore become thinner and weaker. Convex surfaces so-and-sonister be use in intragroup spaces to reduce the impact of sound.Sound waves that reflect from a bursiform surface are very dense and compressed therefore the sound is amplified. Concave surfaces should be avoided in interior spaces as the result is undesirable.Reflection on flat surface Reflection on convex surface Reflection on concave surface3ABSORPTIONWhen sound waves strike a surface some of the sound is absorbed by friction. The materials that absorb are known as absorbants. Absorption in auditoriums or theatre the takes place in three ways In Air This absorption happens due to friction between two molecules though this is very smallBy Audience Cloth is an absorbant. So in theatres and auditoriums the sound is absorbed by the clothes o f the audience. Themore the audience the more the absorption takes place.By furniture and furnishing Materials such as curtains, carpets absorb sound.The following materials are commonly used for absorption of sound Acoustic Plaster This contains shredded insulation material with cementPerforated and Unperforated compressed cane or wood fibre board.Wood Particle board nasty wood woolMineral/ furnish wool matsMineral/ glass wool tilesComposite units of perforated hard board backed with perforated fibreboardRequirements of a good acoustic material-Should have high absorption powerIt should be able to absorb a wide range of frequenciesShould be gaudy and easily availableShould look attractive afterward fixing itIt should be fire resistantShould have adequate structural strengthShould be non- hygroscopic.It should be insects and termites free4SOUND INSULATIONSound insulation/sound proofing is a method used to subdue the level of sound passing through the insulating building component. People generally confuse sound absorption and sound insulation to be the same. The two are very different from each other. Sound absorbents which are mostly pours materials absorb thus reduce the sound which is reflected from surfaces. On the contrary sound insulating construction reduces sound passing through it. Sound absorbers, are poor sound insulators. While hard material used for sound insulation areinferior sound absorbers.TABLE 4.1. SOUND INSULATION BETWEEN ROOMS homeOVERALL INSULATION IN db1. Between living room in one house and the living room in another502. Elsewhere between houses or flat403. Between two rooms in the same house.304. Between two class rooms in a school405. Between two rooms in an office306. Between two wards in a hospital45Impact Insulation- is a rating of how well a building floor reduces the impact of sounds, such as footsteps.Sound Insulating Materials Non porous wet sections- The sound insulation of non-porous rigid constructions such as sealed solid brick masonry ramparts varies. It depends upon the weight per unit area. There is a point when it requires major increase in weightiness to propose small increase in s ound insulation.Porous Rigid Materials Porous cover masonry and clinker concrete are some examples of porous rigid materials. They provide 10 percent higher insulation as compared to non-porous rigid partitions due to their sound absorptive quality. To enhance the results of insulation it is recommended that porous partitions should be plastered on at least one side and if possible then on both sides.Flexible Porous Material These materials provide low insulation. make up lower than rigid materials. Flexible porous materials consists of mineral wool, quilt etc. To increase insulation rigid materials and porous absorbers can be combined in concert and then applied. This will produce better insulation per unit area.4.1WALL INSULATIONWalls are a vertical barrier of sound. Proper construction of walls can increase the level of sound insulation. Construction of walls for sound insulation can be of four types Rigid Homogeneous Walls- Stone, brick or concrete masonry constructions come chthonian this section. The sound insulation in these walls depends upon their weight per unit area. Sound insulation in these increases if the thickness of wall increases. Due to this these walls become uneconomical and bulky after a certain limit.Partition Walls of porous materials- These can be rigid or non-rigid. Rigid porous materials such as porous concrete masonry, cinder concrete etc. increase insulation about 10.%. While partition walls of non rigid porous materials provide very low sound insulation. However they can be used if combined with rigid materials.Double wall partition A double wall partition comprises of Plaster boards Or fibre boards or plaster on laths on both sides. With sound absorbing cushion in between. Rough wooden blocks are provided to support the cushion. Double wall partition is a wall of rigid as well as nonrigid porous materials.Cavity Wall Construction- This is said to be the most adequate wall construction from the sound proofing point of view. In this two walls are made with a gap of minimum 5cm between them. This gab can be left over(p) air filled as we know sound travels the slowest in air or can be filled with some flexible material, exchangeable quilt etc. On the surface of the wall celotex or other insulating board may be fixed.4.2FLOOR AND CEILING INSULATIONLike walls are vertical sound barriers similarly floor and ceiling are horizontal sound barriers. The materials used for the construction of floors and ceiling i.e. R.C.C, stone etc. provide great insulation again air borne noise but do not function well for structure and impact borne noise. The target of sound proofed floors is to provide insulation against impact and structure borne noise.This can be achieved by the following ways-APPLING RESILIANT SURFACE MATERIALS ON FLOOR In this a thin concrete storey is provided as R.C.C floor slab. On top of this then a soft floor finish or covering is applied. This finish or covering can be of linoleum, insulation bo ard, cork, carpet, etc. this helps in reducing impact noises.CONCRETE FLOOR FLOATING CONSTRUCTION This is similar to Cavity wall construction as discussed earlier. In this method we construct an isolated floor from the existing concrete floor. Then a resilient or porous material like glass wool is laid on the R.C.C flooring. On top of this a water proof sheet is put and then a 5cm thick layer of concrete is given. This kind of construction provides complete insulation against impact sounds.TIMBER FLOOR FLOATING CONSTRUCTION In case of wooden flooring the problem of sound insulation is even more. This process is similar to concrete floor floating construction. The only difference is that mineral or glass wool quilts are used for isolation purpose. At times sand or ashes are also used for isolation.CONCLUSIONSound is mechanical wave which travels through a medium. Sound can be pleasing as well as disturbing. Its necessary to emit disturbing sounds to have the perfect required atmosp here. To make an area sound proof its walls/partitions, floor and ceilings need to be treated and insulated. The methods of insulation as discussed above are some ways through which sound proofing can be done. Sound proofing or insulation is the method by which transmission of sound waves can be bard from passing from one area to another.References expression Constructions by B.C Punamia. Sound Insulationhttp//www.meritnation.com/ask-answer/question/how-many-characteristics-a-sound-wave-have.www.scribd.com/doc/102689279/acoustics-ppt