To understand the principles of noise and how soundproofing works, we need to start with some definitions. Noise is unwanted sound. Sound is the physical component and unwanted describes the emotional and psychological effect it has on a person. Home means different things to different people. However, it is often described as a personal and sacred place; somewhere to shelter from the rest of the world.
This is why many people find noise entering their home intrusive and irritating. Not being able to:
- relax in your own home
- read a book
- watch your favourite TV programme
without hearing your neighbours is depressing. Add to that the worry they might hear you and your home could become full of anxiety.
Noise is sound that is created when an object vibrates fast enough that it produces a disturbance in a gas, solid or liquid. This generates a pressure wave in the surrounding air. Sound is the term used to describe the vibrations. They then enter the ear and are interpreted by the brain.
We know you’re sick off noise from your neighbours. It doesn’t matter whether it’s having to listen to their TV over yours, booming music, or a particular tone of voice. Once you notice it, anxiety can build. Not knowing when their music will stop can make you feel uncomfortable in your own home. Noise can also disturb your sleep and cause stress. Ultimately, unwanted noise from neighbours can make you think of moving home.
However, this brief introduction to sound and the principles of noise will give you a better understanding of unwanted noise. It will also help you implement the ideas and concepts of soundproofing your home.
Humans’ sensitivity of sound is affected by three things:
- frequency (or ‘pitch’)
- loudness of the sound
- length/duration of a sound.
Audible Frequency Range
What to do if your neighbours have installed a TV on party wall!
One of the key principles of noise is frequency. Frequency or ‘pitch’ is measured in hertz (hz). Humans can feel rather than hear sounds with a frequency as low as 20hz. A teenager with good hearing can hear a frequency as high as 17,400hz. As we get older we find it more difficult to hear higher frequencies; a normal, middle-aged adult hears up to between 12,000 and 14,000hz. For this reason some convenience shops have started installing devices that emit high-frequency sound. Only teenagers can hear this and therefore it’s thought to discourage them from hanging around inside or outside the shop. The voice of a normal male adult will range between 85 and 185hz and a normal female adult’s voice between 165 and 255hz. The human ear is most sensitive at frequencies between 2,000 and 5,000hz.
Most sounds we hear from neighbours occur within 125 and 5,000hz. Many present-day sound systems can produce low-frequency noise below 80hz and some people have deep voices that will transmit through a house’s structure. At present in the UK, government testing requirements for separating walls/floors to meet Part E of the building regulations only test in the frequency range 100hz to 3,150hz.
The good news is that 8,000hz sounds like a very high-pitched squeal, and most separating walls, ceilings or floors will barrier frequencies this high. These higher frequencies are actually quite easy to keep out through airtightness. High frequencies produce small sound waves that pass through small holes in the structure of your home. Low frequencies produce large sound waves that struggle to get through small gaps in the structure. Very low frequencies, between 20 and 100hz, travel the furthest and are the hardest to stop.
How noise travels is another important aspect of the principles of noise. Airborne noise is noise transmitted through the air, such as TV, radio, music, and conversation. The UK government regulates this to tackle the noise pollution in newly built homes and refurbishment projects through the Building Regulations Approved Document Part E. Builders and developers are required to install sound insulation to the walls, ceilings and floors separating some refurbishments and newly built homes and then have an acoustic test carried out. The building must pass the acoustic test for the new development to meet building regulations. Just like an electrical certificate the acoustic certificate is part of the inspection process. Therefore, inspectors can’t sign off the development without it.
MEASURING SOUND LOUDNESS
DECIBELS: A decibel (dB) measures how loud a noise is.
50dB is quiet while 140dB is so loud it can immediately injure your ears.
Why acoustic tests on new-builds still leave you with noise
Here’s why. The level of sound prevented from transmitting through separating walls and floors is measured (airborne sound insulation). The higher the figure the better. The regulations require a score of at least 45dB Dnt’w +Ctr. The testing covers a wide range of frequencies. Unfortunately, it takes the average of the room. An amazing wall system on the party wall might achieve 70dB Dnt’w + Ctr. But, if you have not treated the suspended floor void, the ceiling void or other holes in the structure, these would let neighbour noise through. If the sound test found the overall sound insulation average of the room to be 50dB Dnt’w +Ctr, which is a pass, you might still be able to make out words and follow conversations from next door.
The acoustic test came into force on 1 July 2003 for refurbishment projects. To give you an idea what 45dB Dnt’w + Ctr means in real life, in a 1950s three-bedroom semi-detached house, Quietco paid an independent company to carry out a UKAS-accredited sound insulation test of the separating party wall before any soundproofing was installed. The sound insulation value of this wall measured at 47dB Dnt,w + Ctr, 2dB. This is higher than the building regulations require for new dwellings. In other words, the sound insulation was better than the standard required for today’s newly built properties. After the testing, I stood in our client’s neighbours’ dining room, the other side of the party wall, and managed to turn on our client’s smart speaker. (See https://quietco.uk/videos/)
When an object hits the structure of a building the sound energy is transferred to the structure and can then transmit through it: becoming a structure-borne sound. So, when your neighbours’ door slams, you hear the impact noise of the door leaf hitting the door frame. You may also hear the door latch (the metal parts of the door) hitting the strike plate on the door frame. Both these impact noises transmit through the structure of the building all the way to your property.
In the early days impact noise was measured by a steel ball being dropped from different heights on to a wooden floor; the higher the drop the more audible it would be in the room below. Later a ‘tapping machine’ was developed. The strict testing practices, standards and methods acoustic engineers have to abide by are outlined in the British Standard for measuring impact noise, BS EN ISO 140-7. The tapping machine uses a series of steel hammers tapping ten times a second. This machine is placed on the sub floor/temporary floor (not a finished or tiled floor) in the source room to be measured; acoustic engineers then measure the calibrated sound pressure in the room below. You can reduce impact noises by isolating the surfaces generating them from the structure. Floating floors, floating walls and suspended ceilings are a few examples.
Principles of noise and your home
The key things you need to understand about the two different types of noise is that both will get into the structure of your home. This structure will then transmit noise to other areas of the house. You can make a room airtight but still hear music, TV, conversation noise from next door because it is transmitted through the structure. These noises will still get through unless you isolate the finished surfaces from the structure.
There is no point in just applying sound insulation to a separating party wall if noise is getting in through the structure: you must apply soundproofing to any area that is connected to the source of that noise.
The impact sound pressure level is called Lnt’w. A maximum level of 64dB Lnt’w for impact noise transmission to separating floors also came into force on 1 July 2003 for converted properties. Confusingly, the lower the Lnt’w figure, the better. Since 1 July 2004 the regulations require airborne sound barriers to be a minimum of 45dB Dnt’w +Ctr for separating floors, ceiling and walls, and impact sound transmission to be a minimum of 62dB Lnt’w.
Reducing noise in your home
If you are a homeowner and want to know more about the principles of noise and how you can deal with noise in your home, then consider reading, ‘The Noise Free Home‘.
Alternatively, if you are within our catchment area, you could benefit from a home visit. This is like a structural survey but for noise. We examine your home and discover where noise in travelling. The first step is to fill out our contact form and book a free noise diagnosis call. It’s time to create a peaceful haven in your home.
© Copyright Jim Prior