Ministry of Noise
Your definitive guide to noise from Metropolitan Insulation.
What exactly is noise? Noise is pollution that affects everyone, but unlike other forms of pollution, once it stops, it completely ends leaving the environment 100% free of it.
How people perceive noise is hard to quantify. For some, a particular noise may be enjoyable, whereas to others it may be a nuisance and annoys. This is particularly true of loud music. So in short, noise is subjective, enjoyed by some and unwelcome by others and considered a form of pollution.
It’s widely acknowledged that too much noise can be a danger to health - hearing may be affected - whilst also causing stress and anxiety, sleeplessness and other symptoms.
How is noise measured?
Noise is measured in decibels, ranging from 0dB barely audible, through to levels of noise that hits the pain threshold at around 140dB.
0dB Just audible
30dB Gentle conversation
55dB Female speaking
59dB Male speaking
80dB Sports car interior
90dB Road drill (3m away)
100dB Busy factory
140dB Pain threshold
Any noise of 80dB + in volume is not only unpleasant and uncomfortable, but may impair hearing. Although it’s not just the volume… lower levels of noise can be especially irritating, especially at night when you are trying to sleep.
Noise nuisance can be eliminated at source, thus giving instant relief. If this isn’t possible, then soundproofing or sound insulation is the answer to reducing the noise pollution.
How does sound travel?
Like the ripples in a pond after a stone has been thrown in, sound travels through the air in spherical ripples, reducing in intensity as they move further from source. Sound absorbing materials provide a barrier that dissipates the energy, reducing noise.
Noise that is airborne, including speech. Airborne noise is one of the most irritating of nuisance noises.
Noise caused by vibration is often a nuisance - generating flanking noise and airborne noise too, depending on location.
Flanking noise is typically perceived in flats or other multi-occupied buildings where noise transmits through the fabric of the building. If walls are of a lightweight construction this is more problematic – new build flats meet rigorous specifications to reduce flanking noise today.
Both airborne and impact noise that usually transmits through the fabric of a building – typically problematic through walls that penetrate floors or walls that timber suspended flooring is fixed to.
Impact noise is generated when things come together – a door slamming, heavy footsteps etc. Hard floors in flats may contribute to a lot of impact noise for neighbours below.
The Noise Reduction Coefficient – this defines how much sound specific materials absorb. It is the average sound absorption between 250Hz - 2kHz rounded to the nearest 0.05.
Materials with different NRC ratings audibly alter a room. The lower the NRC rating, the lower the sound absorption.
Part E stipulates that 10% of all new dwellings should be Pre-Completion Tested on-site for audibility between separating walls and floors between dwellings only.
Proprietary Systems are those developed and tested by manufacturers using specified components that achieve a certain level of performance.
Robust Standard Details
A series of Government approved performance tested solutions considered to satisfy Part E.
Sound absorption is usually needed in enclosed areas like halls, studios and recreation spaces to reduce noise reverberation (echo). For instance a hall without insulation may be unsuitable for many events because of excessive reverberation, making speech difficult to hear and especially problematic when people are further apart.
Also known as a sound blocker, a sound barrier typically comprises insulation with a high mass that reduces the amount of noise that can travel through it.
Imagine a river with a large rock in it - water flows quickly around it but leaves a slack area immediately behind it. Sound waves follow exactly the same action when presented with a sound barrier that is not complete. That’s why a fence between gardens can act as an effective sound barrier.
This is usually required to minimise noise from resonating panels. Sound damping involves gluing on a vibration pad to stiffen panels and reduce nuisance noise.
The term for reducing noise level(s) being heard. It is not always possible to completely silence a noise – soundproofing reduces the intensity of noise pollution as much as is technically possible.
The 1/3rd octave Sound Transmission Losses measured above (ASTM - American) are referred to as Sound Reduction Indices (R)
by the European ISO standards.
The SRI value has been developed to approximate the performance of a material in reducing the transmission of speech. Bear in mind that the SRI value does not offer accuracy with respect to non-speech sounds eg music, traffic etc.
STC is the American ASTM, standard E413, equivalent of SRI - based on the averaged sound insulation achieved between 125Hz and 4kHz.
As above, please note that the STC value has been developed to approximate the performance of a material in reducing the transmission of speech only.
Soundproofing terms and explanations in Plain English!
Rating for the airborne sound insulation of a material or building element in a laboratory.
Measurement of the airborne sound insulation between two rooms.
D'nT,w + Ctr
As above, with the low frequency correction factor included.
Measurement of the impact sound insulation of floors.
Unit measuring the relative strength of noise. A decibel is one tenth of a ‘bel’ - this is also a unit used for measuring the intensity of noise.
How does Sound Travel?
Sound travels according to the medium, air being the most common. Sound travelling through air usually originates from somewhere in space – eg someone's mouth. Waves travel in spherical ripples (similar to water waves).
Transmission Loss (TL)
Transmission Loss rates the ability of a material to block sound - usually measured in 1/3 octave band intervals.
A material’s Transmission Loss (TL) is measured by mounting a sample in an opening of a wall separating two reverberant test rooms. One room plays Broadband noise (source) and the difference in sound levels in this room and the other is defined as the Noise Reduction (NR). Material density is directly related to Transmission Loss.
Any questions? Please contact Metropolitan Insulation Services for more details and proven soundproofing solutions.