Acoustics and Sound Insulation of Buildings

ACOUSTICS AND SOUND INSULATION

Acoustics is the science of sound, which deals with origin, propagation and auditory sensation of sound and also with design and construction of different building units to set optimum condition for producing and listening speech music. Acoustic property of building is based on acoustic nature of building materials and how sound is transmitted through the adjacent structural elements. Noise is unwanted sound, that is considered as a nuisance in buildings for residential or domestic purposes. The buildings must possess good sound insulation property to have good acoustic feature. Sound insulation of buildings is a property that must be considered in the initial stages of planning. Planning for the structural elements, to make them sound proof is one of the consideration.

Sound insulation is a kind of measure to prevent the sound waves from permeating. It is demonstrated by the sound transmission loss which is expressed by the difference of decibels between the incident sound and permeated sound. The sound insulation property of building materials is the ability in the reduction of sound across a partition. For a good conventional office building construction, the sound insulation is experienced well when it is in the range of 45dB. The unwanted and unexpected sound is always considered to be a noise and that really is a question of the acoustic property of the building.

FACTORS AFFECTING ACOUSTICS OF BUILDINGS

❖ Site selection - Site of building should be away from market area or densely populated areas to avoid origin of sound.

❖ Volume and shape of building - Both factors should be designed and calculated as per the location of site and purpose of building.

❖ Interior spaces and planning - Internal division of spaces should be as per function and purpose of building. Circulation of people should also be considered.

Construction Materials and Technology

❖ Height of building - Height affects the reflection and reverberation factors of acoustics.

❖ Function and purpose of building - Whether residential, commercial, public hall, recording studio, institutional, etc.

ACOUSTIC PROPERTIES OF BUILDING MATERIALS

It is always necessary to have a pre-planning, mainly for the building constructions that are prone to noise disturbances. Awareness about the acoustic properties of building materials to some extent would help us to have a right choice on the material to be selected when acoustics is a concerned factor. Acoustics properties of some of the materials are explained below:

❖ Acoustic properties of Masonry, Concrete or Stone materials: Mass and rigidity property are the two factors that make a material to be highly noise resistant. The concrete wall is highly efficient than masonry. Masonry material made floor or wall do perform appreciably. Massive materials like stone, concrete can stop high sound waves that are less resistant to less massive materials. Concrete slabs do perform well in the sound insulation activity.

❖ Acoustic properties of Wood and Related Products: These are less dense than masonry. They have a smaller performance in sound isolation. Woods are more massive, hence they are added to certain interior walls to increase the massiveness. Plywood, which is used in multilayer in interiors, is used to make it sound proof. It can reflect sound which can be considered as an important property for sound treatment. It resonates easily which promotes absorption of sound, some of which pass through the material and some reflects.

❖ Acoustic properties of Steel: Based on performance and structure, steel is one of the best materials for sound insulation. Because of high cost, it has less application. It is highly dense and massive in nature. Steel carries the sound through vibration within the material. This sound transfer is called as the structure-borne vibration. The normal case is airborne vibration which is not appreciable.

❖ Acoustic properties of Glass & Transparent materials: The glass is massive in nature. There is a new development of absorptive glass-like materials that have the property to absorb more sound waves instead of reflecting. The material is made as a transparent foil thinner in nature with tiny holes. Their application comes in sound studios.

❖ Acoustic Insulating Materials: Foam, fiberglass, rock wool etc. can be considered as the familiar insulating materials.. The fiberglass material gains higher sound absorption property. These materials absorb sound by reducing the velocity of particles that carry the sound waves in the air. Under low velocity, the pressure is high. Now wood materials absorb more sound at high pressure. Sound waves gain higher pressure at room boundaries. So, care must be taken in the arrangement of boundaries or walls.

❖ Acoustic Properties of Rubber and Plastic: The known materials are vinyl, neoprene etc. These materials are used to make low cost economical acoustical devices. But their use is almost considered limited. They can be used as mechanical isolators for floating glass, by preventing vibrations of the diaphragm to be transmitted to the walls.

ADVANTAGES OF ACOUSTIC IN CONSTRUCTION

The advantages of acoustics in construction are:

❖ Accurate sound frequency and intensity can be achieved

❖ Privacy of space is maintained without any disturbance

❖ The cost of extra acoustic material used in interior can be reduced

❖ More carpet area can be utilized with proper planning and designing

❖ All acoustical factors are studied and considered right from designing process of a building

❖ In auditorium, acoustic planning results in evenly distribution of sound, seating arrangement contributes to absorption of sound, uneven thickness of wall surfaces results in reflection of sound