Sound proofing is a fairly technical and specialist area and there aren’t that many companies that are very capable of it. We have had the help of Custom Audio Designs to help prepare this project (which they are sponsoring), so that we can ensure that you get the information you need from trade experts actually working in the soundproofing industry.
Noise regulation is controlled by the Building regulations in Part E – Resistance to the passage of sound which you must adhere to at all times during your soundproofing project.
Why do we need Soundproofing: How sound travels through walls, floors and ceilings?
Sound is a form of energy. The more energy produced in one place, the greater effect that energy will have in another if it is allowed to get there.
Example: Fire a pea from a catapult = Energy expelled. Get hit by the pea = Energy received!!
The further the catapult elastic is stretched, the more force delivered to, and by the pea, the more the pea hurts when it hits it’s target. The pea is like sound here – the more noise that is created the louder it will be at the point your receive it or hear it. It’s all pretty straight forward so far.
If you can stop the pea being fired (or the noise being made) there are three ways of stopping the pea hurting:
- Wear something very thick or dense, and then the pea will bounce off. You may feel the dent where it hit, but its effect will be reduced. This is because the energy produced by the pea will be absorbed and quickly reflected by the dense material and no vibration will occur to allow the energy (and pain) to spread into the body. The same happens if you close the door between you and the sound and it is block, at least in part
- Wear something very thick and soft, the power of the pea will again be absorbed by the softness. You may still feel the pea, but the force will be greatly reduced. The same happens to sound when you put your head under a pillow – the sound is deadened.
- Take the catapult away from the maniac firing at you!!
The same principles can be applied to sound. Unfortunately its a little more complicated because the different frequencies (Bass, etc) of sound, produce different energies and need to be dealt with in slightly different ways. If we return to the pea analogy, a very sharp, small and pointed pea delivered with a lot of energy, it may well pierce the protection, whereas a larger, flatter missile would not. A giant pea would do a different kind of damage, but you need protection from both. In the same way you need to protect your home from both high and low frequency sounds.
Soundproof Barriers and Passive Absorption Soundproofing
There are two main sound control options although they come with many variations:
Passive Absorption Soundproofing
When sound passes through materials that are designed to absorb the sound, such as mineral wool insulation or acoustic foam, the sound waves cannot pass directly through as they are forced to change directions many times as they pass through the material. These are known as “acoustically absorptive materials”. The sound waves are forced to travel greater distances along the loose fibres of the material, changing directions numerous times, in order to pass completely through the absorptive material. Each time a sound waves changes direction, a portion of the energy is absorbed as it is converted to (very small amounts of) heat. This reduces the amount of sound energy and there the amount of sound you can hear.
Low frequency sound (bass) travels much further than high frequency sound as it finds it easier to travel around barriers if it has the chance. This is why you can hear thunder from miles away. If living anywhere near a music festival, it is the bass noises you can hear for longer the further away you get. This is because the amplitude of the sound wave is bigger.
When there is a reflective surface behind the absorber, (such as a wall) the sound energy which passes through the absorber will be reflected back and through the absorber once again. Absorbers work best when there is some sort of a reflective surface behind them. For some sounds (low frequency) an air gap is ideal between the absorber and the reflective surface or wall.
Low frequency sounds have less energy than high frequency sounds and (although they travel at the same speed) cannot travel as far, through absorptive layers, as higher frequency sounds.
A noise barrier can be constructed from almost any non-porous material. Since sound is energy, an effective barrier must have enough mass (weight and density) and a low resonant frequency to stop (or reflect) this energy rather than just vibrate with it. As sound pressure levels increase so does the sound power (amplitude and energy). High sound power levels will excite any surface they encounter causing the surface to vibrate at its resonant frequency which inevitably makes the walls shake.
Low frequency sound contains more energy, because a larger volume of air is being displaced to produce the long wavelengths associated with bass and sub bass frequencies. These low frequency sounds easily excite most common building materials like wood and 12.5mm thick plasterboard.
Soundproofing and Noise Pollution for Tenants and Landlords
If you are a tenant in a semi detached house, bungalow or flat and you are suffering from noisy neighbours, bad traffic noises or any other form of noise pollution you can get some help from Landlordzone.
If you want to find out more about sound and soundproofing in general there is some good information on Wikipedia.
Soundproofing Solutions in the Home
For retrospective soundproofing, the solution at a generic level, is to retro-fit acoustic boards or layers of some kind to either deaden, reflect or absorb the energy waves. We have broken this problem down into the three main areas of problem soundproofing and defined the methods used to deal with the specific problems encountered in each situation. For each method an acoustic membrane can be used as well as other methods mentioned.
How to Soundproof Solid Walls
The first principle of reducing sound travelling through solid walls, which already have a good mass, is to add more mass. Sound finds it much harder to travel through tightly packed (and therefore heavier) material and the mass simply deadens the sound. Ideally we would cover solid walls with lead sheet but apart from being incredibly expensive, decorating would be a nightmare!
Adding a dense layer to solid walls will reduce sound considerably and there are some very good, dense plasterboard and other acoustic boards on the market to assist with this.
How to Soundproof Hollow, Stud and Plasterboard Walls
Sound hits a hollow, or stud wall and then travels across the top layer (plasterboard) to the fixings which attach it to the studs, or upright timbers, in the wall. The sound then vibrates these timbers passing the sound through to the other side of the wall. In an ideal world one would take off one side of the wall and add an acoustic layer of mineral wool inside the wall to absorb the sound. When putting the plasterboard back it would be great to decouple the boards from the studs in some way to stop the vibration on the board reaching the studs.
If you are building your own partition stud and plasterboard wall then all of the soundproofing precautions mentioned in this page can be used.
Decoupling is possible by adding vertical bars, called resilient bars, to the studs and fixing the boards back on onto the bars, rather than directly onto the studs. This isolates the sound from the studs and lowers the vibration through the wall. These bars are called resilient channels.
Resilient bars are thin metal channels which effectively isolates the plasterboard from the studwork, eliminating ‘direct contact’ to dissipate sound which would normally be transferred through the frame. This system is easy to install and produces excellent results especially when used with suspended high mass ceilings
Decoupling, or isolating the wall surface from it’s studs can cause some problems with resonance however and using this method is always improved with an acoustic absorber placed inside the wall void.
All the solutions above are only available if you are happy to pull your wall apart and create all kinds of mess. However there are now very thin materials called mass loaded barriers, usually made of vinyl, which can be fixed to the surface of an existing stud wall to deaden sound. There are also sheets of acoustic plasterboard which can be fixed over the existing wall to create further sound barriers. Ideally a mass loaded barrier would be sandwiched between 2 sheets of acoustic plasterboard to create an even more effective sound barrier.
Soundproofing walls that are hollow, such as the stud wall can be a tricky job and getting a reasonable level of isolation will usually involve implementing several different techniques all used together.
Acoustic plasterboard or Soundbloc™ boards are blue in colour and are of a higher density than normal plasterboard. They are either 12.5 or 15mm thick and available from most builders merchants.
How to Soundproof Ceilings
Most ceilings are constructed in a similar way, and therefore transmit sound in a similar way, to that of hollow, or plasterboard stud walls. The noise coming through a ceiling is obviously being transferred from the floor above (see soundproofing floors, below) so decoupling the ceiling is a good way to stop sound reaching the ceiling covering. While decoupling and adding resilient bars (See soundproofing hollow plasterboard stud walls) it is good to pack mineral wool insulation into the void. When doing this however, remember to place all electrical cables into conduit to avoid the cabling getting too warm.
Mass loaded barriers and other soundproofing mats can also be fixed to the ceiling, either in the same operation as changing the ceiling surface to soundbloc plasterboard or straight onto an existing ceiling. The soundproofing mats are usually about 2mm thick and made of very dense materials which simply absorb the sound when it hits them.
If you have access to the floor above, then see the section on soundproofing floors to make the whole ceiling and floor construction as sound-proof as possible.
How to Soundproof Floors
The major reason for wanting to soundproof a floor is to stop the airborne noise from below coming up through the floor. If it is possible to get the floor up by removing and relaying floorboards then adding an acoustic quilt or acoustic mineral wool will greatly assist in stopping the noise. Filling gaps in floorboards will also help although this is far more effective at stopping drafts than sound.
A high performance composite acoustic quilt provides far superior performance to the normal cavity products available as it combines acoustic fibreglass absorption with an acoustic dense membrane to block the sound.
Acoustic mineral wool is very useful in absorbing sound and for the reduction of noise in partition walls and/or between flooring joists and ceilings, especially suspended ceilings. The density of this material is generally at least three times that of standard loft insulation so it’s much more efficient at absorbing sound.
A very quick and efficient acoustic solution which, in effect is a carpet underlay. It is also cost-effective as it can be installed by any home improver or DIYer quickly and easily. See our project on how to lay carpets and underlay. The Quietfloor product reduces both impact noise (banging on the floor through footsteps etc) and airbourne noise coming up from the room below.
Quietfloor works best with acoustic wool in the floor void also but is very effective on its own. It is a quilt made of a dense layer of acoustic foam covered by a very dense layer of 2mm mass load barrier.
How to Soundproof a Workshop, Music Room or Recording Studio
If you wanted to reduce noise in a room where the noise was likely to be very intrusive, including noisy children’s bedrooms, special acoustic foam tiles can be stuck to all surfaces. These acoustic foam grade tiles are CNC cut 25kg / m3 high density foam which has an open cell structure giving optimum acoustic performance.
How to Stop Sound Travelling along Pipes, Cables and Heating Ducts
Baffles can be fitted within airbricks and chimney flues which are no longer used. The baffles or diffusers allow the air through but either reflect or dissipate the noise.
Using acoustic pipe insulation wraps is great for reducing the sound which can travel long pipes and ducts. Some pipe and duct systems can be very noisy and using a macerator system such as Saniflo with a water or waste pump can reverberate through the house. Even some soil and vent systems can be noisy when chains are flushed and gurgling in the basin wastes conjoined with water hammer from badly fitted water systems, can all be reduced greatly by using a dense insulation covering.
A foil faced Acoustic Pipe Wrap for a wide range of applications. Ideal for noisy pipes, pumps, engines, enclosures, saniflow systems, soil pipes etc.
Decoupling the vents and ducts from the surface they are connected to is also useful. As is inserting dense washers (which can be made out of dense foam material such as a yoga mat).
Soundproofing Materials and Products
There are a range of materials suited for soundproofing, many that we have already mentioned, but here are the most common that are used. There are specific characteristics and uses for these various products, which are explained in more detail here:
High Performance Acoustic Membrane
2Kg High Performance Acoustic Membrane that is more efficient than a sheet of lead at blocking sound transmission. Rated at 22dB an only 1.2mm thick it’s easy to work with, easy to cut, and easy to install.
High Performance Acoustic Quilt
A high Performance Acoustic Quilt Provides far superior performance to standard cavity infill products as it combines acoustic fibreglass absorption with our acoustic membrane to block the sound.
Acoustic Mineral Wool
Acoustic Mineral Wool is useful as a sound absorbing material for infilling as it will reduce airborne noise, particularly behind partition walls, in between flooring joists and in suspended ceilings. It is the density of this material that makes it so it’s much more efficient at absorbing sound. It is generally at least three times that of standard loft insulation; the mass of standard fibreglass loft insulation is generally only around 20Kg/m³ whereas acoustic mineral wool would be in the region of 100 – 140 Kg/m³.
This is a carpet underlay system designed to improve both the impact and airborne noise transfer through floors. The laminated composition provides maximum performance for minimum thickness and combines excellent sound insulation with all the qualities of a good carpet underlay. It is quick and easy to install and is easily cut and shaped. Overall thickness is just 12mm so it minimises the increase in floor level. This is a product that can be fitted relatively easily yourself.
A Resilient Bar is a thin metal channel designed to substantially improve the sound insulation of plasterboard walls and ceilings. The channel effectively isolates the plasterboard from the studwork, eliminating ‘direct contact’ to dissipate sound which would normally be transferred through the frame. This system is easy to install and produces excellent results especially when used with suspended high mass ceilings.
Sound Proofing Mats
Sound proofing mats are designed to reduce the airborne noise transmission through lightweight floor and wall structures. Only 2mm thick and again better than lead at blocking sound.
All project content written and produced by Mike Edwards