5.0 Introduction
Noise is unwanted sound. In order to limit the effects of unwanted sound the standards intend to improve the resistance of building elements to sound transmission. Research has presented clear evidence that noise can indirectly contribute to a range of health issues such as stress and anxiety.
Inadequate sound insulation can impair health by allowing noise from other people to disrupt normal life. A number of people in attached homes complain of neighbour noise. The World Health Organisation has established a relationship between noise exposure and sleep disturbance. However, the short or long-term effects are still not clear. Over the years, several pieces of legislation relating to noise (see clause 5.0.9) have been introduced which provide some degree of control of ‘noisy neighbours’.
Noise generated within a dwelling, to some extent, is under the control of the occupants but can still create tension within a family. The provision of sound absorption between rooms should allow people a degree of privacy as they go about their everyday activities.
The purpose of the standards in Section 5 is to limit the transmission of sound to a level that will not threaten the health of occupants from sound transmission emanating from attached buildings and a differently occupied part of the same building. They also cover sound from within the same dwelling if occupants are in rooms where they would expect to have some degree of peace and quiet.
It is important to recognise that the standards will not guarantee freedom from unwanted sound transmission. The standards aim to limit the effects from sound levels created from normal domestic activities, but not from excessive noise from things such as power tools, audio systems inconsiderately played at high volume or even raised voices. The standards do not address environmental noise through the building facade from sources such as aircraft, trains, road traffic or industry. Other legislation covers these areas and further information may be obtained from Planning Advice Note PAN 1/2011 ‘Planning and Noise'.
Home improvements were previously not considered an issue, whereas some can now create a noise nuisance. For example, lifting carpets and replacing them with laminate flooring can have an adverse affect on sound transference in buildings, and particularly on occupants of flats. A leaflet giving further information on home improvements is available at http://www.scotland.gov.uk/topics/built-environment/building/building-standards.
The following is a summary of the main changes that have been introduced since 1 October 2010.
-
Standard 5.1 - removal of guidance regarding the phased introduction of sound tests; and references made in guidance to 'Robust Details (Scotland)'.
-
Standard 5.2 - guidance on sound insulation level between rooms in dwellings.
There are a number of terms used in this section some are included below, these and other useful terms are included in Annex A of the Example Constructions.
Airborne sound is sound which is propagated from a noise source through the medium of air. Examples of these are speech and sound from a television.
Airborne sound transmission is direct transmission of airborne sound through walls or floors. When sound energy is created in a room, for instance by conversation, some of the energy is reflected or absorbed by room surfaces but some may set up vibrations in the walls and floor. Depending on both the amount of energy and the type of construction, this can result in sound being transmitted to adjacent parts of the building.
Direct transmission refers to the path of either airborne or impact sound through elements of construction.
DnT,w is the weighted standardised level difference. A single-number quantity (weighted) which characterises the airborne sound insulation between two rooms, in accordance with BS EN ISO 717-1: 1997.
Flanking transmission is airborne or impact transmission between rooms that is transmitted via flanking elements and/or in flanking elements in conjunction with the main separating elements. An example of a flanking element is the inner leaf of an external wall that connects to the separating ‘core’ of a wall or floor.
Impact sound is sound which is propagated from a noise source through a direct medium. An example of this is footfall on a floor.
Impact sound transmission is sound which is spread from an impact noise source in direct contact with a building element.
L’nT,w is the weighted standardised impact sound pressure level. A single-number quantity (weighted) to characterise the impact sound insulation of floors, in accordance with BS EN ISO 717-2: 1997.
Rw is a single number quantity (weighted) which characterises the airborne sound insulation of a building element from measurements undertaken in a laboratory, in accordance with BS EN ISO 717-1: 1997.
The reduction of sound transmission from attached buildings, or part of the same building, and sound from within the same dwelling can be provided through different mechanisms which involve; mass, isolation, absorption, resilience and stiffness (see annex A of the Example Constructions). Wall and floor constructions that provide a combination of such mechanisms generally provide better sound insulation.
Good design incorporates at least 2 or more of the above mechanisms and can reduce a range of sound frequencies typically found in attached dwellings.
The effects these variables can have in predicting both sound transmission and insulation are as follows:
-
through a heavyweight wall or floor it is its mass per unit area. A reduction in sound transmission and increase in sound insulation are expected with increasing mass, as the heavier the wall or floor, the less it vibrates in response to sound waves and hence the less sound energy is radiated. For example, heavyweight constructions such as masonry cavity walls provide mass and isolation
-
through a lightweight wall or floor it is the use of cavities, isolation and absorption. A reduction in sound transmission and an increase in sound insulation are expected by the use of cavities with fewer and less stiff connections, while absorptive material hung in the wall cavity will absorb mid to high frequency sound energy. The formation of narrow cavities, such as dry linings on dabs, can also create an unwelcome ‘drum’ effect at low frequencies and filling or lining them with absorbing material can help to reduce this. For example in lightweight constructions such as timber frame walls, the twin stud of the timber frame provides isolation, stiffness and absorption
-
resilience is needed for separating floors in flats where there is direct vibration impact such as footfall noise. Resilience reduces the impact vibration by dynamic movement and also converts the energy into heat. Examples of resilient elements for floors include floating floor treatments such as battens and cradles, resilient bars and resilient floor coverings, other than carpet
-
mass and stiffness help to reduce significantly low frequency sound transmission whereas absorption and resilience predominantly reduce mid and high frequency sound transmission
-
isolation has the most influence over all frequencies of sound but can be limited by structural connections such as wall ties, straps and fixings that may bridge isolated leaves or elements.
When sound waves strike a wall or floor, the pressure variations cause the construction to vibrate. A portion of the vibrational energy on the sound source side will be transferred through the wall or floor where it is radiated as airborne sound on the other side. There is a loss in sound transmission as the frequency of the incident sound (sound waves produced from striking against a wall or floor for example) increases. This also varies with the direction of the sound waves, and is usually assumed to be the average for all possible angles of incidence.
Impact sound is sound that is spread from an impact or vibrational source in direct contact with a building element such as a floor. A structural vibration is transmitted from the point of impact through the structure causing vibration leading to the radiation of sound into an adjacent room below. In a building this is commonly caused by an object hitting the floor, from where the vibration is transferred into the structure. Usually the vibration path will lead to the ceiling and perimeter walls below. The amount of impact sound heard below will depend upon many factors including the force of the impact, the vibration transmission characteristics of the floor construction and the floor covering.
Flanking sound transmission occurs when there is an indirect path for sound to travel along elements adjacent to walls and floors. If the flanking construction and its connections with the separating structure are not correctly detailed, flanking transmission can equal, or even exceed, sound levels perceived as a result of direct transmission. Flanking transmission can occur, for instance, when a wall abuts the face of the inner leaf of an external cavity wall, and the walls are insufficiently tied or bonded together, thus allowing the noise to travel along the inner leaf.
Listed below are some pieces of legislation and guidance that may be relevant and/or helpful to those using the guidance in this particular section.
The Common Law of Nuisance recognises that an occupant has the right to the free and absolute use of the property, but only to the extent that such use does not discomfort or annoy a neighbour.
Part IV of the Civic Government (Scotland) Act 1982 sets out a range of public nuisance offences.
The Environmental Protection Act 1990 as it relates to noise, states that ‘any premises in such a state as to be prejudicial to health or a nuisance ranks as a statutory nuisance’.
The Human Rights Act 1998 (as it relates to noise) Article 8 guarantees the right to respect for private and family life.
The Antisocial Behaviour etc. (Scotland) Act 2004 empowers the local authority to serve a warning notice in relation to noise which exceeds the permitted level.
The Planning Advice Note PAN 1/2011 ‘Planning and Noise', provides advice on the role of the planning system in helping to prevent and limit the adverse effects of noise.
Scottish Ministers can, under Section 7 of the Building (Scotland) Act 2003, approve schemes for the certification of design or construction for compliance with the mandatory functional standards. Such schemes are approved on the basis that the procedures adopted by the scheme will take account of the need to co-ordinate the work of various designers and specialist contractors. Individuals approved to provide certification services under the scheme are assessed to ensure that they have the qualifications, skills and experience required to certify compliance for the work covered by the scope of the scheme. Checking procedures adopted by Approved Certifiers will deliver design or installation reliability in accordance with legislation.