Acoustic insulation and soundproofing insulation may sound similar; however, they serve different purposes. One is used to manage sound within a space, while the other is designed to prevent sound from entering or leaving it.
Poor sound insulation can result in disturbances from neighbours at home, colleagues in adjacent offices at work, pupils in neighbouring classrooms at school and many more instances. This can lead to increased noise pollution and a loss of privacy, both of which can be avoided through the correct specification of sound insulation.
High levels of internal noise can cause disturbed sleep, reduced concentration and impaired speech intelligibility. Inadequate sound insulation therefore has a direct impact on comfort, wellbeing and performance.
A CIEH Noise Survey report[1] published in March 2022 highlighted the health effects of noise, stating: “Sufficient undisturbed sleep is necessary for daytime alertness and performance, quality of life and health. Sleep disturbance is one of the most harmful effects of environmental noise exposure. The short-term effects of noise-induced sleep disturbance include impaired mood, increased daytime sleepiness and impaired cognitive performance.”
In this blog, we will examine acoustic insulation and soundproofing insulation in more detail, comparing and contrasting their functions. We will also explore the relevant regulations and standards that apply when specifying acoustic materials and identify which insulation products are best suited to either acoustic control or soundproofing applications.
What is the purpose of acoustic insulation?
Acoustic insulation is designed to manage and improve the sound within a space. It does not stop sound from entering or leaving a room; instead, it controls how sound behaves inside the space. Acoustic insulation works by absorbing sound waves and reducing reverberation.
Acoustic insulation is used where the quality of the sound is a high priority such as office spaces, classrooms, lecture theatres, concert halls and auditoriums.
Types of acoustic insulation includes, but is not limited to:
- Acoustic wood fibre underlays
- Acoustic foam
- Wood fibre insulation for door panels
What is the purpose of soundproofing insulation?
Soundproofing insulation, often just referred to as sound insulation, is designed to prevent sound from entering or leaving a room. Its purpose is to create a barrier that stops sound waves from travelling through walls, floors and ceilings to reduce noise pollution for the room’s occupants and help to enhance their acoustic comfort.
This type of insulation is especially useful in settings where controlling noise is essential such as within party walls between dwellings, in pitched or flat roofs to dampen the noise of falling rain, or in separating floors to reduce the sound of people walking on the floor over a room below.
Types of soundproofing insulation includes, but is not limited to:
- Dense wood fibre boards
- Wood fibre batts
- Mineral fibre slabs
How does an insulation material control sound or reduce its transmission?
To understand soundproofing materials and how they function, it is important to recognise that sound is a form of energy. Sound travels from its source and, as it moves, it creates vibrations in the air and in any objects it encounters. These sound waves eventually reach the listener’s ears, where they are processed by the brain.
With acoustic insulation, people are in the same room as the noise source. The insulation materials used are generally porous and designed to trap sound and help improve sound quality by preventing sound waves from reflecting around the room and creating echoes.
By contrast, where soundproofing insulation is used, the people that are likely to appreciate its presence are usually in a separate room to the sound source. In this case insulation is used that can add mass to the adjoining walls, floors or ceilings. This extra mass helps to dampen sound vibrations and increase the structure’s ability to block sound.
What building regulations and standards cover acoustic and soundproofing insulation?
The requirements for resistance to the passage of sound in England are set out in Approved Document E of the building regulations. This document defines the performance standards for airborne and impact sound that separating walls, floors and stairs in houses, flats and other residential accommodation must achieve to demonstrate compliance. It also includes provisions for controlling reverberation in the common areas of buildings containing flats.
Pre-completion sound insulation testing is a mandatory requirement under Part E for new homes and conversions. This testing assesses party walls and floors for airborne and impact noise in order to confirm that the required standards have been met before final finishes, such as carpets, are laid.
As an alternative to testing, buildings constructed in accordance with the separating wall and floor details contained in the Robust Details Handbook[2] are deemed to comply without the need for further testing.
Approved Document E also provides guidance for schools and directs readers to Building Bulletin 93: Acoustic Design of Schools – performance standards[3], which sets out the required values for sound insulation, reverberation time and internal ambient noise.
How thick should acoustic insulation be to be effective?
The thickness of acoustic insulation required to deliver the sound quality required in a space will depend on several factors including the size and shape of the room along with its intended use as well as the type of acoustic insulation being considered. Rather than specifying based on thickness, the declared acoustic performance of the acoustic insulation should be the focus of its suitability.
Soundproofing materials are rated according to their ability to absorb sound, as measured by the sound absorption coefficient. This coefficient, commonly referred to as the alpha value (α), ranges from 0.0, indicating no sound absorption, to 1.0, indicating total sound absorption. Understanding these ratings is essential when selecting suitable materials for effective soundproofing.
There are two main types of alpha value. αp (practical alpha) relates to sound absorption at a specific frequency. αw (weighted alpha) represents an average across a range of frequencies, providing a more general indication of a material’s sound absorption performance.
Acoustic insulation can be measured to determine the level of sound reduction it can provide in specific situations, such as floors. This is determined by following BS EN 16283-2 – Acoustics. Field measurement of sound insulation in buildings and of building elements – Impact sound insulation[4]. The impact sound reduction of a material indicates the number of decibels by which it reduces sound.
For example, STEICO Ecosilent wood fibre underlay for laminate and parquet flooring can improve the room acoustics by up to 19 dB[5].
How thick should soundproofing insulation be to be effective?
As with acoustic insulation, thickness is not the primary factor when specifying soundproofing insulation. However, because it is commonly used in applications such as party walls to reduce sound transmission, there is a relationship between its thickness and density that influences its performance.
Increasing the thickness of soundproofing insulation lengthens the path through which sound must travel, reducing its energy and enhancing the sound absorption performance of the material it passes through.
Increasing mass is also an effective method for reducing the transmission of airborne sound.
The "Mass Law[6]" states that for every doubling of the mass per unit area of a wall, the sound insulation performance of the wall will increase by 6 dB. Adding mass is also important for reducing low-frequency (bass) noise[7], as its long wavelengths require significant inertia to impede their transmission. Therefore, where low-frequency noise is a concern, increasing mass can be particularly beneficial.
Can acoustic and sound insulation be retrofitted?
Yes, acoustic and sound insulation can be retrofitted to walls, floors, doors and roofs. The key is to add the appropriate type of insulation depending on the acoustic results required.
Where acoustic insulation is needed to improve the sound quality within a room this can be achieved by retrofitting the insulation to the surface of the walls and ceilings.
Where soundproofing insulation is required to reduce noise transmission between rooms, additional mass can be introduced using products such as acoustic plasterboard or dense wood fibre panels. Similarly, rigid wood fibre boards can be added to existing roof structures to help improve acoustic performance.
Where can I find out more information about acoustic and soundproofing insulation?
STEICO offers a range of wood fibre insulation boards and batts that add density and can provide effective sound absorption across a variety of wall, floor and roof applications. In addition, STEICO supplies wood fibre underlay products for laminate and parquet flooring, as well as wood fibre softboard for door panels. Together, these products can help support specifiers seeking to enhance the acoustic performance of buildings.
To enquire about using our acoustic insulation on your next project, contact us and our expert team will be happy to help.
[1]www.cieh.org/media/6561/cieh-noise-survey-england-2020-21.pdf
[2]https://www.robustdetails.com/patterns/
[3]www.gov.uk/government/publications/bb93-acoustic-design-of-schools-performance-standards
[4]knowledge.bsigroup.com/products/acoustics-field-measurement-of-sound-insulation-in-buildings-and-of-building-elements-impact-sound-insulation-2
[5] www.steico.com/tds_steicoecosilent_gbr-irl_en
[6]www.auralexchange.com/knowledgebase/mass-law-in-acoustics/
[7]pollution.sustainability-directory.com/learn/what-is-the-relationship-between-the-mass-of-a-wall-and-its-ability-to-block-low-frequency-noise/?