Category: Special Services in Buildings

These materials are made out of mineral wool or glass wool. The coefficient of absorption varies which depend on the thickness of the board or mat, density, perforations, mode of fixing and frequency of sound.

The material can be formed by combination of mineral wool and cement asbestos or with mineral wool and hard board. The coefficient of absorption for the first combination is about 0.95 and for the latter is 0.20. Such boards are generally suspended from trusses.

Straw boards, pulp boards and compressed fibre boards have varied coefficient of absorption. These boards can be fixed by ordinary panelling. The thickness is about 17 cm and coefficient of absorption varies from 0.17 to 0.50.

These are commercially available materials with adequate absorbent qualities. The absorption of sound is uniform and most suitable for small rooms. But it is costly compared to other acoustical materials.

It is a granulated insulation material mixed with cement. The quantity of cement used in such materials is to provide enough strength and have sufficient pores. The coefficient of absorption varies from 0.15 to 0.30.

Common building materials are absorbents of different levels. Such materials are called as absorbent materials. Table 28.3 Acoustics level and reverberation time Table 28.4 Optimum reverberation time for closed area Qualities of a good acoustical materials are as follows: Some of the acoustical materials are discussed below.

The acoustical design of an enclosed space is basically depend on the behaviour of the reflected sound. Due to the reflection of sound two main defects are developed, viz., echoes and reverberation. 1. Echoes Echo is said to be produced when a reflected sound wave reaches the ear just when the original sound from the…

The behaviour of sound plays an effective role in the acoustical design of different types of buildings and in the sound insulation process. A sound originating from a source, such as music or operation of machine, is transmitted through the medium in all directions. The transmitted sound strikes on some surface, like wall, ceiling, floor…

Sound can travel through some medium like air. It can not travel in vacuum. Thus for the sound to be audible to the ears, the sound source and ear must be connected by an elastic medium like air. The characteristics of audible sound are discussed below. 1. Frequency of Sound Frequency of pitch of sound…

Sound is produced when part of the atmosphere is compressed suddenly. It is transmitted in the form of waves. The waves are a series of compressions and rare factions created in the air medium. The average sound travels at a speed of 340 m/s at ordinary temperature. It depends on the medium through which it…