Sound proof construction! Characteristics
Sound Proof Construction
- Some materials having hard, rigid including non-porous surfaces, provide the least absorption, whereas these which are flexible, soil porous also can vibrate, and absorb more extra sound
- The efficiency of the sound absorption depends upon the porosity of every material used essentially sound absorbent
- The term used to express the percentage of the incident sound that can be absorbed by a material is known as the absorption coefficient of the material
- If the absorption coefficient of a material is 0.75, means that the material is capable of absorbing 75 % of the incident sound
- Each absorption coefficient changes with the frequency of every incident sound
- low-density materials have a higher absorption coefficient
Classification of Absorbents
- Porous absorbents
- Resonant absorbents
- Cavity resonators
- Composite type of absorbents
- When sound waves strike the surface of a porous material, a part of the waves make reflected while a component enters the pores of the material including dissipated within heat energy
- These efficiencies of this sort of absorbent increase with the increase in the resistance granted by the material
- It is used to absorb sound having a high frequency
- Some absorbent material is fixed toward sound framing timber with an air space between each framing including the wall near the back.
- Such an arrangement runs most efficiently during absorbing sound waves at a base frequency
- This principle of sound absorption is that sound waves of the appropriate frequency cause sympathetic vibrations in the panel which serves to be a diaphragm
- Some absorption of sound uses placed under the dampening of some sympathetic vibration.
- The dampening effect of this system can be improved by placing a porous material in the air space.
- It essentially consists of a chamber with a narrow opening (entrance) in which absorption takes place by the resonance of the air in the chamber which gives a loss of sound energy
- Such an arrangement container work effectively over a single picked frequency.
- Application of cavity resonator is usually restricted to absorption from an individual machine or in similar cases
Composite type of absorbents
- They consist of perforated panels mounted on battens to leave a cavity between the panels and the wall at the back
- The panels may be of metal, wood (plywood) hard broad, plasterboard, etc
- The range of holes in the panel should differ between 10 to 20 % of each total area of the panel.
- When some sound strikes the panel, the sound waves pass through the holes and also get damped through the resonance of the air in that cavity.
- The effectiveness of that system can be increased by placing a porous material same mineral wood etc. in this cavity
- This type of absorbent is commonly used, as it is easy to install, economical and it can accommodate a wide range of frequencies
Characteristics of audible sound
There are three characteristics of sound
- Intensity & loudness
- Frequency & pitch
Intensity & loudness
- The intensity of sound is defined as the amount of flow of wave energy crossing per unit of time through a unit area taken perpendicular to the direction of propagation.
- Some loudness about sound is described as the degree of sensation.
- Which is not a wholly physical quantity but partly subjective & does not depend upon the ear & listener.
Frequency & pitch
- Frequency or pitch is defined as the number of cycles that a sounding body makes in each unit of time.
- It is a measure of the quantity of sound.