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Soundproofing is a solution to effectively control or combat unwanted noise, and in this article we discuss how to soundproof a wall correctly.

Whether it’s homeowners looking for peace and tranquillity from noisy neighbours, hotels to ensure guests get a good nights’ sleep, offices to maintain corporate secrets in meetings and conference rooms, or businesses which need to reduce the noise impact they make on surrounding areas; soundproofing comes with a long list of causes and solutions.

When it comes to soundproof a wall, most people will have either little understanding of what they’re trying to achieve or conversely, get so bogged down with trying to become an expert.

As such, they become even more confused and end up never achieving anything of notable results.

You don’t have to be an acoustic consultant to successfully soundproof a wall, but a basic knowledge of sound as well as a fundamental understanding of available soundproofing solutions is always a good place to start.

To understand how soundproofing works, it is important to mention that sound is a form of energy.

Sound travels from a source, whatever that may be, and during the distance it travels causes vibrations whenever it hits air and any objects in its path.

These sound waves then reach the recipient’s ear drums which stimulate the brain.

Soundproofing solutions work to reduce the sound pressure created from the source to the receptor.

In this in-depth article, we’ll explore a wide range of essential factors on how to correctly soundproof a wall and to get you the best possible results on your soundproofing project.

Clarify Your Objectives

Although it might sound fairly obvious, firstly ask yourself a few simple questions as to what you are trying to achieve.

For example, what is the source of the sound or in other words – where precisely is the noise coming from?

Perhaps the aim is to contain a noise source and prevent it from breaking out into neighbouring rooms or areas.

Maybe the aim is to prevent external noise from outside coming in to an area, known as noise ingress.

If you have a loud home cinema installed, then the aim here is both.

You’ll want to prevent the sound from the A/V system from being heard in other rooms or even your next door neighbours.

You’ll also want to prevent noise ingress, which are the noises created outside the cinema which may compromise the enjoyment of the film.

Such examples are hearing your neighbour’s TV through the wall, their feet stomp up and down the stairs, a phone ringing, conversations and arguments, or even their washing machine during the spin cycle.

So it’s clear, there’s lots of things that can cause noise whether from within your own home or a neighbouring property.

Find Your Weak Points

One of the key tips to remember is that sound travels at an amazing speed, some 340 metres (1200 feet) per second.

In many respects, although somewhat faster, it is similar to water as it will exploit the path of least resistance and use any means possible to travel from A to B.

So with that in mind, your acoustic treatment will only be as strong as its weakest point.

Therefore, ensure that your approach is foolproof and fit for purpose and that your soundproofing solution is applied correctly to prevent any obvious and direct pathways where noise could ‘trickle’ through.

Air gaps or air bricks for example, ventilation systems and ducting, steel structures, columns or corner posts, lintels and structural supports can all be weak points offering flanking routes for sound to travel between walls.

Types of Noise

Airborne

Airborne noise or airborne sound is defined as any sound that is transmitted by the air, like music or speech.

Sound waves are picked up and carried by air until they crash into something solid, like a wall.

The collision sends vibrations through the wall and into the space beyond it.

Structural Airborne

Structure-borne sound results from an impact on, or a vibration against a part of a building fabric resulting in sound being radiated from an adjacent vibrating surface.

A typical example of structure-borne sound is footsteps on a staircase which can be heard through your neighbouring wall.

Impact

Impact sound (or impact noise) is a form of structure-borne sound that occurs when an object impacts on another, resulting in the generation and transmission of sound.

The structural vibration caused by the impact results in sound being radiated from an adjacent vibrating surface.

Understanding Building Structures & Common Problems

Understanding the different types of buildings, building fabrics and how a noise is reaching you is of great importance.

In other words, learning about how the sound energy is moving from its source to receiving point.

This will determine the type of acoustic installation required to soundproof a wall.

Direct passage, whereby sound travels through the air, via gaps and holes is a very common problem.

For example, a masonry wall will offer a dense structure however its own density will also work against you.

This typical structure would require a framing system of one type or another such as a stud frame or battening to be installed to enable a suitable platform for soundproofing materials to be applied.

Where load bearing walls are concerned, flanking transmissions can occur through the structure of the building itself.

Steel columns, as well as services, pipes, and soil stacks can all successfully circumnavigate acoustic treatments.

Dot and dab plasterboard fixing methods are very common in modern house construction.

The term ‘dot and dab’ refers to the way plasterboard or drywall is adhered to a wall with dots of plaster and in effect stuck to the wall.

Invariably this method is used as it is a very quick, easy and cheap method of levelling a surface for immediate decorating finishes.

However, despite its apparent benefits it can be installed crudely producing several unfilled cavities behind the plasterboard.

This allows for easy passage of sound behind, which acts like a sound box, increasing resonance and amplifying the original source noise like a drum.

It can be particularly problematic if it is installed before a separating ceiling, creating a common cavity all the way up the building.

Types of Soundproofing Principles

Acoustic Isolation

Acoustic Isolation is the prevention of sound leakage or sound ingress, to or from a particular area into another.

For example from an external source, outside to inside, or from one room or dwelling into another room/dwelling.

This can incorporate multiple approaches depending on any given situation, however they will invariably be based around four key principles.

1. Deflection
   Mass, dense materials built into a building’s fabric to increase density and push back sound from where it came. This principle is invariably always going to be used in some way, somehow as simply the finishing board of choice for rigidity or the brick wall in the first instance. However, whilst this principle is good to use, one has to remember that the mass, dense material obviously has rigidity which can and will work against you as a flanking pathway. Certain sound waves will pass through the material and into whatever it is attached and keep on going.
2. Absorption
   Open cell materials that can allow sound waves to enter the material and slow down the energy thus reducing the sound power and sound pressure of the initial source. Always a material/principle that is used as a part fill within any void created by a framing system. The depth is going to be dictated by the depth of the structure or materials used to create the cavity – depth of battens or stud work type of frame. Whilst useful to part fill any dead space to offer some sort of absorption and possible thermal benefit, this type of material really has to be super thick to achieve any higher levels of sound insulation, especially with lower frequency sound waves, which invariably defeats the object as it massively increases the thickness of the entire assembly.However, if you have the chance to incorporate some thickness of absorption into the build, it is good to do so not only for sound absorption but critically to prevent any additional acoustic resonance or regeneration that would happen in a cavity that is left as a complete open void.A bit like small caves……… big no no!
3. Conversion
   Uniquely Acoustiblok Insulation Membrane. When sound waves contact our membrane it vibrates the molecules of the materials which in turn creates friction which is cleverly converted to a trace heat energy. Thus the material works by converting a more problematic acoustic energy into a less problematic heat energy which is simply transferred through the material sideways to reduce flanking transmissions. In any serious or advanced strategy to isolate sound this is an absolute must to work in tandem with the other principles. At only 3mm thick, the depth of the materials are hardly noticed in the great scheme of things but the benefits to uplift acoustic performance are immense.
4. Decoupling
   Separation and decoupling of one side of the assembly to the other by way of a batten or resilient channel invariably installed perpendicular to the main frame and sometimes in conjunction with isolation bracket or clip in which to house the batten. The principle of this not only reduces the direct mechanical fixing/linkage of the system therefore reducing the resulting flanking transmissions within the rigidity of the structure, but also provides an opportunity for a service chamber and a structural platform on which the chosen finishing system can be mechanically attached.

Acoustic Calibration

Acoustic Calibration is to balance or equalise the internal acoustics within a room to optimise quality of sound which will improve the listening experience.

Calibrating a room to reduce reverberation and distortion to achieve cleaner, audible and balanced sound waves can incorporate a number of differing systems or solutions, but they will all tend to work on the basic principle of increasing absorption within the room and specifically the surfaces such as walls, floor, ceiling and therefore reducing reflection, deflection, regeneration.

1. Absorber Panels
   AcoustiCloud Ceiling and Wall Panels
2. Baffles
   A sound baffle is a construction or device which reduces the strength (level) of airborne sound.Sound baffles are a fundamental tool of noise mitigation, the practice of minimising noise pollution or reverberation.
3. Diffusers
   Diffusers are used to treat sound aberrations, such as echoes, in rooms.
4. Isolators
   Vibration isolators often referred to as ‘spikes’ not only reduce vibration, but also lessen noise by preventing unwanted regeneration/resonance.
5. Soft Finishes
   Soft Furnishings to surfaces such as carpets where appropriate, wall fabrics, drapes, curtains and soft furnishings such as seats, sofas, cushions and rugs can all help absorb sound energy.

Applying Correct Construction Techniques

Use the right construction techniques and materials, or a mixture of all the available options for the best possible outcome.

This is where an understanding of the problem and the situation you have will start to dictate the type of solution and materials you can use.

At this point you can start to see a return to previous questions, but will now be able to determine the correct approach.

Deflection

Use of differing mass and dense materials usually as the main structure and finishing materials.

Materials 

• Concrete – typical wall and floor construction
• Masonry – typical wall construction
• Sand/Aggregates
• Mass Loaded Vinyl – rubber impregnated with mass to increase weight and density
• Plasterboard – differing thicknesses and densities depending on the stiffness and purpose and often applied in multiple layers to achieve higher ratings
• Dense sheet materials – ply, particle board

Absorption

Use of differing open cell materials within cavities or open spaces which allow for sound to be absorbed.

Materials

• Open Cell Fibres – natural fibre, mineral wool, stone wool
• Soft Furnishings – quilt or blanket

Thermal Conversion

Materials

• Uniquely Acoustiblok sound insulation membrane – as sound waves impact, the molecules of the membrane vibrate causing friction which in turn converts to heat. Simple and very thin with the highest acoustic effect mm for mm. Converting a problematic sound energy into a less problematic trace heat energy.

Decoupling

Use of system/materials to separate the mechanical linkage of the structure to minimise the direct connection from the front to the back/one side to the other.

Materials

• Resilient Channels – secondary decoupling usually used from source side
• Acoustic Clips/Brackets
• Staggered Stud Construction as an example with timber/steel stud

Soundproofing a Wall

Up to this point, we’ve covered numerous aspects including understanding core objectives, identifying weak points, the types of noise typically created, common building structures and soundproofing principles; as well as calibration and construction techniques.

All of these areas are critical before pressing ahead with your soundproofing project.

Now that we have covered these bases, we can now move onto soundproof the wall in question.

Soundproofing Masonry Walls

This type of wall structure is already giving you a certain level of mass and density, so this is already working in your favour.

To increase the acoustic value and to be able to add materials, a framework is required.

This frame offers a decoupling principle and can be either attached to the existing masonry wall, or built in front of the masonry wall as a decoupled framework being secured at the top (ceiling) and the bottom (floor).

This decision will determine the thickness of the frame or structure to be built.

If attached to the existing wall, which offers excellent structural support, the frame can be thinner from around 25mm depth upwards.

If freestanding, it will need to be a thick enough frame to support itself and be structurally sound.

The cavity or space between the frame should be filled with an open cell material which offers absorption.

Acoustiblok 3mm Insulation Membrane is a good example, which would now be applied to offer the conversion principle.

This would be attached to the front of the framework and secured in way of staples, collars, or self tapping screws, and sealed and tape jointed.

It is advised to minimise fixings and mechanical linkage used to a sensible level.

At this point, it’s possible to either attach a dense finishing board of choice through to the original frame or incorporate an additional cross batten or resilient channel to further decouple the structure.

This then provides a platform onto which to attach the finishing board by way of mechanical linkage/fixings.

An additional measure, which is quite widely used, is to incorporate a second board on staggered junctions to add more mass however, this invariably does not add a huge increase in acoustic noise reduction.

All heads of fixings should be countersunk and a nib of silicone sealant applied to the head to soften and reduce impact and flanking transmission as much as possible.

Soundproofing Stud Walls

This structure requires pretty much the same process as masonry walls, however will be self supporting and can take on slightly differing approaches.

Whether a single stud structure or a double stud structure, Acoustiblok is attached to one side which would usually be the noise source side of the stud or where possible, incorporated to both sides for extra effect.

Again all heads of fixings should be countersunk and a nib of silicone sealant applied to the head to soften and reduce impact and flanking transmission as much as possible.

Essential Finishing

To ensure your installation is sound tight, it is vital to use the correct acoustic sealants, acoustic caulks, jointing tapes and acoustic putty pads to seal and repair penetration and obvious holes or areas of weakness.

Applying the same basic principles of acoustic soundproofing to doors, door frames, and windows will also be essential in reducing obvious weaknesses.

This may be achieved with lining doors themselves with Acoustiblok for example, as well as increasing the size of beading around a door frame or introducing acoustic gaskets to slow down possible air flow and sound ingress through your wall installation.