*2.1.1 Types of absorbent materials*

Various types of absorbent materials are available in the market under different trade names. The value of coefficient of absorption is supplied by the manufacturer. The choice of the absorbent material should be made after carefully considering various factors such as appearance, cost, workability, flame resistance, durability, and light reflection. Following are some of the common types of absorbent materials:


**105**

*Noise Transmission Losses in Integrated Acoustic and Thermo-Fluid Insulation Panels*

materials. They are most suitable for rooms in which small area is available for

4.Strawboard: this material can be used as absorbent material. With a thickness

5.Pulp boards: these are soft boards which are prepared from compressed pulp. They are not expensive and can be fixed by ordinary paneling. The average

6.Compressed fiberboard: this material may be perforated or unperforated. The average coefficient of absorption for perforated board is 0.30 and for the

7.Compressed wood particle board: this material is provided with perforations and it can be painted also. With a thickness of about 13 mm, the average

8.Perforated plywood: this material can be used by forming composite panels with mineral wool and hardboard. It is generally suspended from trusses. The average value of coefficient of absorption for the former composite panel is

9.Wood wool board: this material is generally used with a thickness of 25 mm

10.Quilts and mats: these are prepared from mineral wool or glass wool and are fixed in the form of acoustic blankets. The absorption coefficients of such quilts and mats depend on the thickness, density, perforations, mode of fixing,

When the sound waves are non-periodic, irregular and of short duration, they produce a displeasing effect and such a sound is known as noise. Thus a noise is an unwanted abrupt sound of complex character with an irregular period and ampli-

Following are the important effects of noise: (i) noise creates uncomfortable living conditions; (ii) prolonged exposure to noise may result into temporary deafness or nervous breakdowns; (iii) it is observed that noise has an influence on blood pressure, on muscular strain and even on sleep; (iv) noise leads to fatigue and consequently, the efficiency of persons exposed to noise decreases considerably; (v) it is an established fact that reduction in noise increases to a great extent the output of labor; (vi) presence of noise takes away the essence of music and speech.

Any type of noise is transmitted to the room through walls, floors, ceilings or conduits. The origin of transmitted noise may be air-borne or may be due to impact. Air-borne noise can be transmitted to the receiving room in two ways: (i) by air path between two rooms such as doors, windows, ventilators, key holes, ducts,

unperforated board is 0.52. It has a density of 0.30 g per cm3

, it possesses a coefficient of absorption

.

. The average value of coefficient of

*DOI: http://dx.doi.org/10.5772/intechopen.93296*

of 13 mm and density of 0.24 g per cm3

value of coefficient of absorption is 0.17.

of 0.30 at 500 cycles per second.

coefficient of absorption is 0.40.

and it has a density of 0.40 g per cm3

nature of backing and frequency of sound.

tude originating from a source of non-periodic motion.

about 0.20.

absorption is 0.20.

**2.2 Noise and its effects**

*2.2.1 Transmission of noise*

acoustical treatment.

materials. They are most suitable for rooms in which small area is available for acoustical treatment.

