Soundproofing: What It Is, How It Works & How To Do It

Noise pollution is a growing problem for billions of people across the globe who are far more likely to live in busy cities than our ancestors were.

The primary problem with excessive noise is that it can cause poor sleep which can lead to a myriad of problems which impact every area of your life.

Noise can cause hearing problems and sleep disorders which in turn can lead to health problems such as high blood pressure, stress-related heart issues and mental health problems.

Excessive noise can also cause irritation and an inability to concentrate.

As populations grow and more and more people live in greater proximity to one another the need for effective soundproofing is growing.

What is Soundproofing?

The dictionary definition of soundproofing is “to prevent sound from coming into a room or building, or from being heard outside it”.

The golden rules of soundproofing are:

  • If air can get through then noise can also get through too.
  • Minimise vibrations as much as possible.

Soundproofing is all about making amendments to the physical structure of a property so that vibrations and airborne sound are dispersed and absorbed efficiently.

How Does Soundproofing Work?

Soundproofing works by tackling the two ways in which sound travels.

The most common way that sound travels is as air-borne sound, this occurs when soundwaves, caused by something like someone speaking or music being played, travel through the air.

The second way sound travels is as impact noise, this is when sound vibrations travel through a solid structure such as floorboards.

Soundproofing Against Airborne Noise

Airborne noise is noise that travels through the air.

Someone talking, a radio or TV playing are examples of common airborne sounds.

Airborne noise can be a problem in homes where you have thin internal walls which are poorly insulated and have gaps in them (for example around plug sockets).

The lack of insulation means the sound can travel freely through the gaps in your wall without being absorbed.

Dealing with airborne noise effectively involves dampening and adding mass. This is done by sealing up walls, doors, floors and ceilings (walls are usually the primary culprit) and adding insulation to prevent airborne noise from travelling through.

Soundproofing Against Impact Noise

Impact noise is noise that occurs when an impact is created and the vibrations carry it through a building.

Examples of impact noise include someone walking heavily on a floor, hammering, doors closing or furniture being moved about.

Impact noise is often a problem in homes where there are uninterrupted connections between rooms.

For example, if you have a brick wall which has no cavity in it then the vibrations can travel directly through from one side to the other.

Dealing with impact noise involves creating small gaps (decoupling) to disrupt the flow of the vibrations.

Adding rubber insulation (adding mass) to absorb any remaining vibrations is also crucial to soundproofing against impact noise.

Ideally, as many methods as possible should be employed in any soundproofing project to achieve the most optimal results.

How Much Noise Is Too Much?

The table below gives a rough indication of how loud some common noises are measured in dB.

dB is the common unit used to measure sound. 0dB is the quietest sound a human ear can hear. Calm breathing is 10dB which is 10x as loud as near total silence.

Leaves blowing in the wind is not (as you might imagine) 20x as loud as near total silence, it is in fact 100 times as loud.

Someone whispering at 30dB is 1,000 times as loud.

This is because decibels are measured on a  logarithmic scale, this means that the difference between the values increases as the values increase.

The tables below give insight into how a change in decibel levels might sound in real life:

10 dB Calm breathing
20 dB Leaves blowing in the wind
30 dB Someone whispering
40 dB A stream
50-60 dB A quiet office
50-65 dB A normal conversation
60-65 dB Laughing
70 dB A Hoover
75 dB Dishwasher
78 dB Washing machine
80 dB Road/traffic noise

The human ear is fine with noises up to 85dB in volume. Busy road noise won’t cause any hearing problems, even in the long term.

However even a noise as quiet as 20dB can be irritating particularly if you can hear it when you are trying to sleep.

Thankfully the quieter the noise the easier it generally is to soundproof against it.

85-90 dB Lawnmower
100 dB A passing train
98 dB Farm tractor

Exposure to noises of 90dB and above is fine for short periods however prolonged periods of exposure can, over time, contribute to gradual hearing loss.

Noise of 90dB and above will get through most windows and will make all but the deepest sleepers up. So if you live by a train line, farmers field or lawn that gets regularly cut then soundproofing your windows is a good idea.

Being exposed to noises above 100dB for more than a minute at a time has a high risk of permanent hearing damage.
103 dB Jet plane 100 feet away
110 dB A symphony orchestra
120 dB Thunder
110-140 dB A rock concert
130 dB Jet takeoff

If you live right on the edge of an airstrip or by a popular gig venue then you will probably be familiar with obscenely loud noises.

If you have trouble with any noise above 100dB it is very important that you take your soundproofing seriously and do everything you can to reduce the impact of it.

Exposure to sounds above 100dB for more than a minute can quickly lead to permanent hearing loss.

Soundproofing Methods

There are many different soundproofing methods which can be used to reduce sound pressure.

Some common soundproofing methods are:

  • Increasing the distance between you and the noise
  • Creating a room inside a room
  • Deflecting the soundwaves
  • Dampen the soundwaves
  • Absorbing the soundwaves
  • Noise cancellation systems

Increasing The Distance Between You And The Noise

It makes sense, the further you are away from the noise the quieter it sounds. Unfortunately, in many cases this isn’t a viable soundproofing solution however if your noise problem is caused by something like a noisy generator moving it further away from your home (and maybe even housing it in a well soundproofed shed) will make a big difference.

a red and black petrol generator

Sound pressure and sound intensity both decrease as the distance from the source of the sound increases.

As a rough guide, sound levels will drop by 6dB whenever the distance between the sound source and the sound receiver is doubled, so moving your generator from right outside your house to 20m away should make it completely inaudible.

Creating A Room Inside A Room

The room inside a room method of soundproofing is said to be by far the most effective way of soundproofing any room.

The ‘inner room’ and the ‘outer room’ both have solid walls which are decoupled to prevent vibrations from travelling through.

Decoupling

Decoupling is a method whereby walls, floors or ceilings are fitted in a way which prevents them from directly touching anything which vibrations could travel through such as another wall, a floor joist or a ceiling joist.

This is often achieved by using something called resilient channels. These clip to your joists and the plasterboard is then attached to the resilient channels.

Resilient channels contain small winding riveted channels inside them which the soundwaves travel through, this means that sound energy has to travel very far to make it into your plasterboard.

Using resilient channels quickly uses up sound energy meaning that very little sound will make it through the wall or ceiling.

Decoupling can also be achieved used between your wall and the floor by installing rubber pads underneath your wall.

Green glue can also help decouple walls and floors as it creates a rubber seal between surfaces which deadens vibrations.

Adding Mass

Mass blocks sound, plain and simple.

If somebody shouts at you through a curtain (even if it’s a soundproof curtain) you will hear them, if somebody shouts at you through a wall it will be much quieter.

Adding mass to your wall or putting mass between you and the source of the sound will deflect soundwaves, the more mass the more deflection will happen and the less likely soundwaves are to travel through the wall.

Deflecting Soundwaves

Sound deflection is a method of soundproofing which is often used outdoors in yards or gardens.

It is a good strategy to use if you suffer from noise caused by a busy road, train-line or airport.

Deflection works by placing an obstacle between your home and the source of the noise, this bounces the soundwaves away from your home.

a garden wall with flowers in front of it

Outdoor deflection barriers can take the form of fences, walls, a shed, a thick hedge, trees or anything big that obstructs the soundwaves.

Absorbing Soundwaves

Sound absorption is a very common soundproofing practice.

It works by placing a material in the way of the soundwaves, when sound passes through the material some of the sound energy is absorbed and converted into heat energy.

Insulation foam is one of the most effective soundproofing materials for sound absorption, it is commonly used inside stud walls, and beneath floors.

Active Noise Cancellation Systems

Noise cancellation systems (also known as active noise cancellation or ANC systems) are a high tech soundproofing solution. They work by using a microphone to listen to the noise coming in the room using their inbuilt speakers. They then play the transverse noise wave – this is another way of saying the opposite noise.

The result of this is that the sound waves cancel each other out so that your room sounds silent.

This kind of technology is quite expensive and has its limitations, for example, it is best suited to cancelling out predictable rhythmic noises such as the type of sound that may come from an appliance inside your home.

ANC technology struggles with external noise which could be any volume and come from any direction making it difficult to effectively counteract it.


We hope this article has given you a solid insight into what soundproofing is all about and how it works. There is a lot to soundproofing so please browse our website for more in-depth information or don’t hesitate to get in touch with me if you have any specific questions.

Leave a Reply 0 comments