Acousticss and Sound Insulation
Acousticss is the survey of sound. The cognition of this field is necessary as it helps in making peaceable milieus. The proficient knowhow of sound insularity has been helpful in building functional theaters, infirmaries, Auditoriums, jam tablets, etc. Sound is created when a surface vibrates. When this quiver is periodic or rhythmic so the sound produced is delighting to the ears eg. Musical Notes. On the contrary when the quiver is non-periodic and irregular so it is termed as noise. eg. Babies shouting.
Sound travels in the signifier of longitudinal moving ridges. Each moving ridge moves rearward and frontward go throughing on the quiver to the following. For us to be able to hear sound clearly it is really of import for the moving ridges to go uninterrupted. It is proven that sound travels the fastest in solids, so in liquids and the least in air. This is because in solid the molecules are so tightly packed that the transmittal is the easiest. In liquids excessively the molecules are reasonably near to each other where as in air it becomes a small tough for sound to go. Sound can non go in vacuity as it needs a medium to go. The velocity of sound in air depends upon the wet or waterlessness in air. The more the wet the faster sound will go.
CHARACTERISTICS OF SOUND
- Intensity and Loudness of sound:
Loudness is the response of worlds to the impact of sound. Whereas strength is the sum of sound moving ridges go throughing through per unit country per unit clip.
- Frequency and Pitch
Sounds can be of different types and wavelengths. Pitch is
What helps us separate between sounds of same
Loudness but of different frequences. This is the
characteristic whic helps us recognize a man’s voice and
The quality of sound is what enables us to distinguish between two musical tones played on different instruments. A survey has shown that the notes produced by instruments are at times pure notes. They have some cardinal tones of frequence field-grade officer and extra tones of frequence 2fo, 4fo, etc. called over tones. The cardinal is heard really clearly because it has greater impact human ear.
Table 1.1, ACCEPTABLE NOISE LEVEL
|TYPE OF Building||NOISE LEVEL RANGE ( dBs, dubnium )|
|1.Radio and T.V. studio||25-30|
|2 Music Room||30-35|
|3. Hospitals and auditoriums||35-40|
|4. Apartments, hotels and places||35-40|
|5. Conference suites and libraries||35-40|
|6. Class suites||40-45|
|7. Banks and shops||45-50|
REFLECTION OF SOUND
Sound moving ridges from a field surface reflect in the same manner as that of visible radiation. The angel of incidence is equal to the angel of contemplation.
Following are the features of contemplation of sound:
- When sound moving ridges reflect from a level surface the moving ridge foreparts form a spherical form and the Centre of curvature is the beginning of sound
- When sound moving ridges reflect from a convex surface they get magnified and hence become dilutant and weaker. Convex surfaces can be used in interior infinites to cut down the impact of sound.
- Sound waves that reflect from a concave surface are really heavy and compressed hence the sound is amplified. Concave surfaces should be avoided in interior infinites as the consequence is unwanted.
Contemplation on level surface Reflection on convex surface Reflection on concave surface
When sound waves strike a surface some of the sound is absorbed by clash. The stuffs that absorb are known as absorbants. Absorption in auditoriums or theatre the takes topographic point in three ways –
- In Air– This soaking up happens due to friction between two molecules
though this is really little
- By Audience— Cloth is an absorbant. So in theaters and auditoriums the
sound is absorbed by the apparels o f the audience. The
more the audience the more the soaking up takes topographic point.
- By furniture and trappings– Materials such as drapes, rugs
The undermentioned stuffs are normally used for soaking up of sound –
- Acoustic Plaster – This contains chopped insularity stuff with cement
- Perforated and Unperforated tight cane or wood fibers board.
- Wood Particle board
- Compressed wood wool
- Mineral/ glass wool mats
- Mineral/ glass wool tiles
- Composite units of pierced difficult board backed with pierced fiberboard
Requirements of a good acoustic material-
- Should hold high soaking up power
- It should be able to absorb a broad scope of frequences
- Should be inexpensive and easy available
- Should look attractive after repairing it
- It should be fire immune
- Should hold equal structural strength
- Should be non- hygroscopic.
- It should be insects and white ants free
Sound insulation/sound proofing is a method used to repress the degree of sound go throughing through the insulating edifice constituent. Peoples by and large confuse sound soaking up and sound insularity to be the same. The two are really different from each other. Sound absorbents which are largely pours stuffs absorb therefore cut down the sound which is reflected from surfaces. On the contrary sound insulating building reduces sound go throughing through it. Sound absorbers, are hapless sound dielectrics. While difficult stuff used for sound insularity areinferior sound absorbers.
Table 4.1. Sound INSULATION BETWEEN ROOMS
|Situation||Overall INSULATION IN dubnium|
|1.Between life room in one house and the life room in another||50|
|2. Elsewhere between houses or level||40|
|3. Between two suites in the same house.||30|
|4. Between two category suites in a school||40|
|5. Between two suites in an office||30|
|6. Between two wards in a infirmary||45|
Impact Insulation-is a evaluation of how good a edifice floor reduces the impact of sounds, such as footfalls.
Sound Insulating Materials –
- Non porous stiff partitions-The sound insularity of non-porous stiff buildings such as slicked solid brick masonry walls varies. It depends upon the weight per unit country. There is a point when it requires major addition in thickness to supply little addition in sound insularity.
- Porous Rigid Materials —Porous concrete masonry and clinker concrete are some illustrations of porous stiff stuffs. They provide 10 per centum higher insularity as compared to non-porous stiff dividers due to their sound absorbent quality. To heighten the consequences of insularity it is recommended that porous dividers should be plastered on at least one side and if possible so on both sides.
- Flexible Porous Material —These stuffs provide low insularity. Even lower than stiff stuffs. Flexible porous stuffs consists of mineral wool, quilt etc. To increase insularity stiff stuffs and porous absorbers can be combined together and so applied. This will bring forth better insularity per unit country.
Walls are a perpendicular barrier of sound. Proper building of walls can increase the degree of sound insularity. Construction of walls for sound insularity can be of four types –
- Rigid Homogeneous Walls-Rock, brick or concrete masonry buildings come under this subdivision. The sound insularity in these walls depends upon their weight per unit country. Sound insularity in these additions if the thickness of wall additions. Due to this these walls become wasteful and bulky after a certain bound.
- Partition Walls of porous materials-These can be stiff or non-rigid. Rigid porous stuffs such as porous concrete masonry, clinker concrete etc. increase insularity about 10. % . While divider walls of non stiff porous stuffs provide really low sound insularity. However they can be used if combined with stiff stuffs.
- Double wall divider –A dual wall divider comprises of Plaster boards Or fiber boards or plaster on laths on both sides. With sound absorbing shock absorber in between. Rough wooden blocks are provided to back up the shock absorber. Double wall divider is a wall of stiff every bit good as non–stiff porous stuffs.
- Cavity Wall Construction-This is said to be the most equal wall building from the sound proofing point of position. In this two walls are made with a spread of minimal 5cm between them. This chitchat can be left air filled as we know sound travels the slowest in air or can be filled with some flexible stuff, like quilt etc. On the surface of the wall celotex or other insulating board may be fixed.
FLOOR AND CEILING INSULATION
Like walls are perpendicular sound barriers likewise floor and ceiling are horizontal sound barriers. The stuffs used for the building of floors and ceiling i.e. R.C.C, rock etc. supply great insularity once more air borne noise but do non work good for construction and impact borne noise. The mark of sound proofed floors is to supply insularity against impact and construction borne noise.
This can be achieved by the undermentioned ways-
- APPLING RESILIANT SURFACE MATERIALS ON FLOOR –In this a thin concrete bed is provided as R.C.C floor slab. On top of this so a soft floor coating or covering is applied. This coating or covering can be of linoleum, insularity board, cork, rug, etc. this helps in cut downing impact noises.
- CONCRETE FLOOR FLOATING CONSTRUCTION –This is similar to Cavity wall building as discussed earlier. In this method we construct an stray floor from the bing concrete floor. Then a resilient or porous stuff like glass wool is laid on the R.C.C flooring. On top of this a H2O cogent evidence sheet is put and so a 5cm thick bed of concrete is given. This sort of building provides complete insularity against impact sounds.
- TIMBER FLOOR FLOATING CONSTRUCTION –In instance of wooden shocking the job of sound insularity is even more. This procedure is similar to concrete floor drifting building. The lone difference is that mineral or glass wool comforters are used for isolation intent. At times sand or ashes are besides used for isolation.
Sound is mechanical moving ridge which travels through a medium. Sound can be delighting every bit good as upseting. It’s necessary to breathe upseting sounds to hold the perfect required atmosphere. To do an country sound proof its walls/partitions, floor and ceilings need to be treated and insulated. The methods of insularity as discussed above are some ways through which sound proofing can be done. Sound proofing or insularity is the method by which transmittal of sound moving ridges can be bard from go throughing from one country to another.
- Constructing Constructions by B.C Punamia. : Sound Insulation
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