MATERIALS FOR ACOUSTICS

The materials used for acoustics can broadly categorized into the following types : Barrier Board Plastering wall and soundproofing Acoustic underlay Soundproofing glue Glass wool insulation Cellulose insulation Natural wool insulation Polyurethane foam insulation Rock wool insulation

BARRIER BOARDUSAGE: Barrier boards, or acoustic boards, are two outer

layers sandwiching a special sound absorbing material.

The outer layers can be made of wood, plaster or some other composite and the inner layer is usually a sponge foam of some kind 

EFFECIENCY:Barrier boards are designed to absorb sound in the high to mid frequencies, and can reduce noise levels by up to 75%.They are good for reducing mechanical sound transmission too very little additional bulk. They are normally used for blocking out traffic noise or isolating a home theatre.

SHORT COMINGS Barrier boards will never totally account for all sound absorption on their own. For additional soundproofing, you may need to install further insulation on the inside or outside of the wall.

PLASTERING WALL AND SOUNDPROOFINGUSAGE:

Plasterboard is used to provide a façade to hide the framing and make solid interior walls.

Where it applies to sound insulation though, the density of the inside core is varied for different application making it tougher

Used in the partition of the frame of two or more subdivided dwelling.

EFFECIENCY: Because it's a rigid material with no absorbing layers, plasterboard is less

effective than other types of sound insulation, Airborne noise, though, can be reduced by up to 15% through a dense core

plasterboard. Where plasterboard is used as an insulating layer between two wall frames though, it can reach over 30%.

SHORTCOMINGS: As a wall material, plasterboard is less effective than other insulation types

because it's a rigid material and will transmit mechanical sound through a frame very well. Between frames though as an insulating layer. Basically used as a substitute for walls

ACOUSTIC UNDERLAYUSAGE: Acoustic underlays are materials designed to sit

beneath floor coverings to dampen sounds that would otherwise carry through the floor.

An acoustic underlay may have a layer of polyester matting as a sound absorber sandwiched between two layers of rubber sheeting, which dampens vibrations.

Acoustic underlays often have additional benefits too - like increasing your floor’s thermal insulation.

EFFECIENCY: Acoustic underlays are able to prevent a good amount of sound from passing

through floors, They are particularly good for dampening footfall and other vibrational noise from passing between floors.

Specialist acoustic underlays can decrease the amount of sound that travels between floors by around 13db-25db.

SHORT COMINGS : Adding more layers of acoustic underlay is rarely a possibility - it would make the

floor too unstable, and raise it too high from the subfloor. Sound transmission can also be reduced while keeping the floor solid without

making it unstable

SOUNDPROOFING GLUEUSAGE: Cheap and versatile, it works by putting extra distance

between two layers of rigid building materials such as plasterboard or OSB.

Sound would typically hit the wall and vibrate it, causing a resonant wave to occur on the other side of the wall, thus passing along the sound.

The addition of soundproofing glue between these layers causes the wave to decay much faster.

EFFECIENCY: It varies because it sits between two layers of other materials, its

effectiveness is dependent on its application. However it is worth noting that multiple layers will increase its effectiveness. It is also especially good at reducing low frequency noise such as the bass

from a decent sound system or explosion sound effects in a home theatre.SHORT COMINGS While not a cover-all solution, there is little reason not to recommend this type

of application for soundproofing. It becomes particularly effective when combined with other forms of acoustic insulation such as sound dampening plasterboard.

GLASS WOOL INSULATIONUSAGE: The way it's made is a bit like the way fairy floss

is spun; molten liquid glass made from sand and recycled glass products is pulled through a superfine mesh by centrifugal force, and the tiny strands dry and cool on contact with air.

The individual fibres are held together with a binding agent, which helps to hold glass wool together and give it strength.

Used in heavy industrial scale mech. noise insulation.

EFFECIENCY: Glass wool batts can help to reduce the transmission of sound, especially

between walls, but their low density allows for more sound to travel through than heavier forms of insulation.

The Rw value for glass wool can range between 25-40, so if soundproofing is important, you will need to look for higher rated batts or another insulation method.

SHORTCOMING: May not be user friendly as the material may be hostile for opertaors

CELLULOSE INSULATIONUSAGE: Loose cellulose insulation is blown into roof

cavities, creating a layer of insulated cover. This type of insulation is one of the most

highly regarded methods of insulating a house.

Cellulose insulation is used as a blow-in insulation for walls in many countries,

EFFECIENCY:Cellulose is a very effective acoustic insulator, with an approximate Rw value of 50+, compared to 36-39 for glass wool (fibreglass) batts. It owes much of its noise blocking ability to its density and lack of air pockets for sound to travel in.SHORT COMINGS:It transfers moisture inside the wall cavity and create mould and dampness.

NATURAL WOOL INSULATIONUSAGE:

Basically used as a substitute to the board family acoustic panels as being a fiber it does not chip away the corners.

Also it is not as irritant as other fiber rolls are used to be and is quiet smooth

Used as a filler material between the barrier board.

EFFECIENCY: Wool is a good sound insulator, though its effectiveness is directly

related to its thickness.  Rw value ratings of around 40 are common for average thicknesses

(approximately 600mm) and increase to 50+ with additional thickness.SHORT COMINGS:Natural wool is a more expensive option in terms of material cost compared to glass wool or mineral wool batts.

POLYURETHANE FOAM INSULATIONUSAGE: The rigid polyurethane foam panel insulation is usually

installed in sheets between the inner and outer wall - or cut to fit in between joists or wall studs in a frame like batts are.

There are two types; open and closed cell foam. Open cell foam relies on air to block the conduction of

heat, while closed cell foam has much smaller bubbles which are not connected to each other and which are filled with a highly thermally resistant gas.EFFECTIVENESS: Spray foam insulation makes for a more effective sound barrier than batts, as

there aren't any small gaps for sound to pass through alongside the beams and joists

Polyurethane is known to be very good at straining out mid-range frequencies (like conversation and loud music).

Specific Rw values will largely depend on what other materials you’re using in wall construction as these will affect the resonance capabilities of the wall as a whole.

SHORT COMING:Spray foam is one of the more expensive options as far as insulation goes - in some cases it's up to 3-4 times the cost of batts

ROCK WOOL INSULATION

USAGE: Installing ROCKWOOL insulation provides a real

reduction in external noise from traffic or neighbours, or internal noise between floors and rooms.

It allow you to design the right acoustic environment for each space, whether it’s a school hall, a concert hall or the rooms of a new home.EFFECIENCY:

Rock wool batts will help to reduce the transmission of sound (especially between walls), but their lower density allows for more sound to travel through than other heavier forms of insulation.

The Rw value for rock wool batts generally range from 25-40, so if total soundproofing is important, you will need to look for another insulation method that's specifically designed for the task.

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