Soundproofing – What is it?

Soundproofing is directly related to noise.

What is noise?

Noise is an unwanted sound. The intensity of noise (it’s loudness) is measured in decibels.

Noise is a cause of stress to many people when it’s occurrence is out of their control. It can cause sleep deprivation or interruption, or maybe just interrupts the enjoyment of your own home and entertainment. With particular reference to domestic situations, noise travels in two forms – Airborne and Structural.

Structural Noise is also known as Impact Noise, and is caused by one hard surface striking another. When a neighbour walks across their wooden floor wearing hard-soled shoes, this can be a cause of stress to those living below or adjacent to them. Structural Noise occurs when the impact travels through the structure of the building allowing the noise and vibration to be felt elsewhere. Structural noise can be difficult to eliminate completely, but can be effectively treated with something like Grei G5 Impact Sound Insulation to reduce the noise to an acceptable level.

Airborne Noise is carried through the air as sound waves. These sound waves make contact with the walls, floors or ceilings, causing them to vibrate. These vibrations cause the air on the opposite side to oscillate, re-creating the sound waves, at reduced volume. Airborne noise is speech, music from a hi-fi, sound from a television, etc. Airborne noise can be very effectively treated with Mustwall Soundproofing Panels, and depending upon the volume and frequency, may be eliminated completely, or at least reduced to an acceptable level.

R’w
Known as the Weighted Sound Reduction Index, R’w is a single number (dB) referring to the ability of a wall or other building structure to provide sound insulation. The higher the number, the better the sound insulation.

L’n,w
Referred to as Weighted Standardised Impact Sound Pressure Level, L’n,w is a measure of the noise impact performance of a floor. It is a field measure of the amount of impact sound reaching a space via a floor. L’n,w is characterised by how much sound reaches the receiving room from a standard tapping machine. The lower the number, the better the performance.

Loudness Comparison Table

Here are some interesting figures, that can help you to understand the volume levels of various sources and how they can affect our hearing.

Loudest Sound Possible 194 dB
Death of Hearing Tissue 180 dB
Jet Take-Off 140 dB
Pneumatic Hammer 130 dB
Pain Level 120 dB
Klaxon 100 dB
Machine Workshop 90 dB
Noisy Pub 80 dB
Noisy Office 70 dB
Human Conversation 60 dB
Standard Home Ambient 50 dB
Silent Bedroom 30 dB
Perceptions of Increases in Decibel Level
Imperceptible Change 1 dB
Barely Perceptible Change 3 dB
Clearly Noticeable Change 5 dB
About Twice as Loud 10 dB
About Four Times as Loud 20 dB

Sound Absorption, Sound Insulation and the Differences Between Them

Sound Absorption
Sound absorption materials are used to minimise reflection of airborne sound by converting sound energy to heat through a frictional process in the absorber. Commonly used sound absorbing materials, such as open celled polymer foams like Acoustic Foam, fibrous layers and slabs of mineral fibre, are porous materials. They can be applied to walls and ceilings to improve their sound absorption properties by minimising sound reflection and thus minimising the amount of reverberation that occurs in the room.

They are used:

Inside ventilating and air conditioning ducts to minimise acoustic reflection on duct walls, thus reducing sound levels inside the duct.
In the cavities of lightweight metal or timber framed partitions to minimise the build up of reverberant sound caused by sound reflections inside the cavity.
In the housing of engine compartments or rooms to reduce acoustic reverberation within.
Sound Insulation
Sound insulation materials are used to minimise the transmission of airborne sound, e.g. from one room to another via a sound insulating wall. Good sound insulating materials are dense heavy materials such as Mustwall soundproofing for walls and ceilings, masonry (brickwork, concrete) and sheet metal. All such materials have a high mass per unit area. Sound insulating materials are also used as noise screens or barriers, e.g. alongside roads, as partitions, walls, floors and ceilings to minimise sound transmission between rooms, and as enclosures around noisy machines.

Although slabs of mineral fibre are very good sound absorbers, they are lightweight materials and therefore poor at preventing transmission of sound, i.e. they are poor sound insulators. Conversely although masonry walls and sheet metal panels are good sound insulators because they are dense and heavy, they have hard sound reflecting surfaces and so are poor absorbers of sound (unless of course they are faced by a layer of sound absorbing material).

How to soundproof a party wall

Soundproofing a Party Wall in a Semi Detached House

Sound transmission through a party wall in a semi detached house is a common problem for many people. It occurs as a result of airborne noise such as human voices, televisions, radios, music performance etc. When airborne sound waves strike a wall, the pressure variations cause the wall to vibrate. A portion of the vibrational energy on your neighbour’s side will be transferred through the wall where it is radiated as airborne sound on your side. There is a loss in sound transmission as the frequency of the sound waves produced from striking against the wall increases. Depending on its loudness and frequency, this noise transmission can be treated either to remove it completely or reduce it to an acceptable level.

How to soundproof a party wall with Mustwall 10
Lay strip of Stywall ST-3 Acoustic Wall Isolation Strip on the floor.
Construct a 50mm metal stud or 75mm timber stud wall independent of the existing party wall.
You should ensure that no part of the new stud touches the face of the party wall.
Use a strip of Stywall ST-3 at sides and on top of the stud where it comes into contact with walls and ceilings.
Fill inside the stud with a high density mineral wool (60kg/m3). This material is commonly available from most builders merchants.
The next step is to fix the Mustwall Soundproofing Panels to the timber frame. You can either apply a single or a double layer.
The Mustwall panels should be butted tightly together and sealed with Stik Adhesive Tape.
Trim the Stywall ST-3 to meet the extent of the Mustwall panels.
Next up, fix two layers of standard 12.5mm plasterboard. Stagger the joints between the two layers.
Leave a 5mm gap around the perimeter of the wall and fill this with Acoustic Sealant.
The soundproofed wall can be finished by plaster skimming or as desired.
Skirting board should can be fixed with a panel adhesive or plasterboard screws.
Leave a gap between skirting board and the floor and fill with acoustic sealant.

How to soundproof a party wall with minimum loss of room space

Soundproofing a Party Wall with a Minimal Loss of Space

When soundproofing party walls in semi detached houses the optimal solution is to construct an independent soundproofed wall. However, this will result in a loss of space of between 100mm – 125mm (4 -5 inches). In todays houses this is often not an option. Mustwall 33B is designed to reduce the transmission of airborne sound with the minimum loss of room space. Using Mustwall 33B the whole system will take up less than 50mm!

Mustwall 33B
Mustwall 33B on a 215mm Block Wall
Rw ( Airborne Sound Transmission Loss) – 59dB

Using the Mustwall 33B thin wall soundproofing system an Rw figure of 59dB can be achieved based on a standard 215mm block party wall.

The system is easy to fit – requiring very liitle DIY experience. See below…..

Installation Instructions

Lay strip of Stywall 45 on floor.
Fix Mustwall 33B to the existing wall using Mustwall plastic fixings.
Fix strips of Stywall 45 to Mustwall 33B as per data sheet. Fix layer of 12.5mm plasterboard to Mustwall 33B using Fix All adhesive.
Stagger the joints between the two layers. Leave a 5mm gap around walls and fill with acoustic sealant.
The wall can be finished by plaster skimming or as desired.
Skirting board should be fixed with glue or plasterboard screws. If using screws ensure that they do not bridge the insulation layer.
Leave a gap between skirting board and the floor and also a gap in the corner. This ensures the wall remains “floating”.
This gap can be filled with acoustic sealant.
The Mustwall 33B system will help reduce everyday noise, that should not normally be heard, i.e. speech radio and televison sound. Excesssive loud music and low frequency noise will still be audible although its overall intensity will be reduced. These situations are better stuited to our independent wall soundproofing system.