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Noise Pollution Issues in Dwellings
Anthony Sneider BA (Hons) M.Phil FIMBM MIMgt MCIM
Building Technologist
It has been estimated that up to four million dwellings in the UK have trouble with noisy neighbours. This paper reviews the growing issue of noise pollution in terms of legal provisions in Common and Statutory Law.
Noise pollution can be described as a health hazard, both in the workplace and at home, yet the law in terms of Health and safety only applies to the workplace. This paper examines the issues of noise pollution in today’s buildings, from the perspective of a building practitioner. In discussing the issue of noise and its pollution in buildings, the topics that will be addressed are, why we need to insulate against noise? How sound insulation is described? What physical characteristics contribute to sound insulation? This paper will review the growing issue of noise pollution in terms of recent legal provisions for noise pollution in Common and Statutory Law, and the importance of quality of detailing/workmanship in the installation of acoustic systems.
BS 8233:1999 page 21.
Prolonged exposure to high noise levels will induce hearing loss. It is for this reason that Health and Safety at work Act requires noise levels in a work place to be limited to less than 90 dB (A) during an 8-hour working day. At a noise level of 105 dB (A), exposure time is limited by the Act to 15 minutes. The following tables describe the range of sound pressure of typical every day noise levels and the way individuals perceive them.
BRE Sound control for Homes 1993 page 6.
Bickerdike Allan Partners.
In the home noise individuals produce can vary dependent on the activity being undertaken, for example vacuum the carpets, washing machine, television, music and now home entertainment systems, which produce noise between rooms can be a nuisance and with modern sound systems the energy output has increased dramatically. The hearing of noise and the fact of being bothered by neighbour’s noise are the key issues that lawyers and courts are dealing with.
Although not a statutory requirement, it is recommended for example, internal walls between bedrooms and toilets or bathrooms should have a minimum noise reduction value of 38 dB. The National House Building Council requirements call for acoustic insulation between bathrooms, toilets and habitable rooms. This action was to reduce the number of complaints from owners regarding the filling of water closets, shower’s etc.
Unfortunately, building design and legislation has failed to keep pace with changing life styles and the demand for privacy, peace and quiet. In statutory law noise is a statutory nuisance under the provisions of the Environmental Protection Act 1990 (EPA). In England and Wales, a local authority’s power comes from Section 80 of EPA. In Scotland the Control of Pollution Act 1974 section 58 and Northern Ireland the Pollution Control and Local Government Act describes the steps, which local authorities are to take, where they are satisfied that a noise nuisance exists.
The main principles established under these Acts are as follows.
a) There is no prescribed level above which a noise becomes a statutory nuisance. Each case is considered on its merits and account taken of the likely reaction of a reasonable person. The noise complained of need not be injurious to health; the criterion can be one of interfering with ordinary comfort or amenity.
b) Where the noisemaker is operating from industrial, trade or business premises, it is a defence to show that the best practicable means to control noise has been used.
In Common law, civil action can be taken against noise nuisance and each case is assessed on its merits. The criterion for civil action is how the noise affects the individual compared with the ordinary inconvenience suffered by the public at large.
Section 80 of the EPA Act 1990, enables the complainant to bring proceedings in the magistrate’s court. Recent actions by Budd v Colchester BC, Mills v Southwark and Baxter v Camden and Pettigrew v Inverclyde Council, have added to the debate on statutory law.
In the case of Budd v Colchester BC (5), the Court of Appeal considered the detail required in an abatement notice on the appellant under section 80 of the EPA 1990. Mr Budd kept six greyhounds at his house, his neighbours complained to the local authority about the dogs barking, particularly in the early hours of the morning.
The House of Lords have considered the case of Mills v Southwark LBC (6) and Baxter v Camden LBC (7). (A common problem between these cases is the everyday noises of neighbours). The case’s centred on the issue of sound proofing in the tenant’s flats or, rather the lack of it.
In the case of Pettigrew v Inverclyde Council (8), a local authority tenant and her two children raised summary applications under section 82 of the EPA, against her landlord and the owner of the property above her. The plaintive was seeking the court to find and declare that a statutory nuisance in terms of the Act existed. The court to make an order against the first and/or second defender to abate the nuisance by provision of adequate sound insulation in the respective subjects owned by them or in the common parts between the properties.
The common issue here is that of inadequate sound proofing between the dwellings. The arguments where based on the fact that the building satisfied building requirements at the time of construction. The occupiers where unhappy with the level of sound being transmitted into their dwellings.
3. How is sound insulation described?
Sound insulation can be described in a variety of ways. The three main situations are, room-to room sound insulation (source is within the building), Impact sound insulation (source is footsteps or other impacts on the building structure) and Outside-to-inside sound insulation (source is in the open air).
The method for the measurement of sound insulation is laid down in BS 2750.
The problem arises with the nature of sound its self. In the case of a floor this can be identified as impact related and airborne sound. Combating this sound transmission requires two forms of acoustic action, which operate in distinct ways – sound insulation and sound absorption.
British Standard 8233: 1999, Sound insulation and noise reduction for buildings, sets out the recommendations for the control of noise in and around buildings and suggests appropriate criteria and limits for different situations.
The Building Regulations 1995, Approved Document E (DoE and Welsh Office) and Scottish Building Regulations Part H, deal with the requirement to protect occupants of a dwelling from excessive noise transmitted from other parts of a building.
Approved document E, page 26.
Sound insulation levels of a building can be tested and figures given for each construction element, such as floors, internal party and external walls.
3.1 Room-to-room airborne sound insulation.
Voices, television sets, hi-fi and musical instruments are all sources of airborne sound. The airborne sound insulation between two rooms can be measured by generating a steady, broad-band sound level in one room (the source room) and measuring the sound-pressure level in both the source and receiving rooms over a range of frequencies.
3.2 Impact sound insulation.
The impact insulation of a floor and its surrounding construction can be tested. The construction is excited by a standardised impact sound source (a tapping machine) and the resulting sound level is measured in the receiving room.
3.3 Out-to-inside sound insulation.
The sound insulation of a building facade can be tested using either road traffic or a loudspeaker as the source of noise.
Now we have discussed the main areas in which sound insulation is required to be addressed in terms of improving the construction of dwellings. We require investigating the physical characteristics that contribute to sound insulation.
4. What physical characteristics contribute to sound insulation?
It is important not to confuse the terms Insulation and Absorption. An absorber such as fibrous quilt will not itself provide much sound insulation, because it has a Low Mass and is permeable to air. Consequently, it is not a suitable material to fill up an aperture through a masonry partition if optimum sound insulation is required. Absorbers can contribute to good sound insulation is installed in the cavity between leaves in double-leaf partitions, where they improve the acoustic isolation between the two leaves (Mass-spring-Mass).
Sound insulation is the main method of controlling the movement of sound within buildings. McMullan (9) in his book on Noise control in buildings identifies the common problems of noise in buildings and gives practical solutions to these problems of unwanted sound.
• Mass.
• Isolation.
• Mass-air resonance.
• Control of flanking transmission.
• Quality of detailing and workmanship.
• Absorption.
4.1 Mass.
The sound insulation of any single-leaf or floor built without gaps depends mainly on its MASS. According to MASS LAW, there will be an increase in sound insulation of about 5dB if the mass per unit area is doubled. In addition, each time the frequency is doubled, a 6dB increase will occur.
For example, the average sound reduction of a brick wall increases from 45 dB to 50 dB when the thickness is doubled.
The critical frequency of a one-brick wall occurs at about 100Hz, and of a half-brick wall at about 200 Hz. The sound insulation of the latter is poorer, not only, because the MASS is reduced, but also because the critical frequency is at a point where its effect is more serious.
Traditionally, construction methods have believed it necessary to incorporate a heavy material into the building fabric in order to achieve a high level of sound absorption to resist the sound energy attempting to pass through it. Doubling the mass of a structure or partition normally reduces the sound transmission by one quarter or 6 dB.
4.2 Isolation.
In principle, double-leaf constructed walls can give better sound insulation than single-leaf wall in part due to MASS, but also due to the way the sound waves encounter two separate masses, whose sound insulation can be added together. In practice, this can occur only if the two masses were completely ISOLATED from one another. In lightweight forms of domestic construction owe much of their sound-insulation performance to isolation.
In resent research by Steel (10), found in developing new light weight acoustic walling products, that the factors effecting performance where;
• Additional mass.
• Stiffness/ Rigidity.
• Separation/ Isolation.
• Completeness/ Airtight.
• Depth of Cavities.
This practical research in an acoustic laboratory has shown the mass-spring-mass theory at work and how sound absorbent materials interact in the construction of acoustic walling. When sound waves come into contact with n absorbent material it enters the material and the energy of the wave is dissipated as small quantities of heat. This is because rather than force the quilt into vibration and form a wave on the opposite side. The fibres within the quilt will move against each other causing friction within the quilt. This action changes the wave (sound) energy into heat energy, weakening the force of the wave and thereby reducing transmission.
4.3 Control of flanking transmission.
The sound insulation between two spaces depends not only on the sound transmitted through the intervening wall or floor, but also on FLANKING TRANSMISSON. This sound travels along any elements common to both rooms.
If flanking constructions are not correctly specified, flanking transmission can equal or even exceed direct transmission and degrade the overall result. Flanking transmission is a complex matter, not only is the construction and size of the flanking element significant, but also is any interaction between it and the wall or floor. The specification of a sound-insulating wall or floor is incomplete if not accompanied by an appropriate flanking construction specification.
4.4 Quality of detailing and workmanship.
A wall or floor will give its expected sound insulation only if it and the surrounding construction are built without faults. Some possible faults are:
• Areas of low sound insulation; for example, gaps or holes in the wall or floor, areas of Low Mass.
• Mechanical bridging of isolation; for example, unwanted-ridged connections such as nails through floating floors or the selection of incorrect wall ties in the cavity.
• Acoustic coupling between the leaves of a double-leaf partition; for example, omission of a specified absorbent quilt or the specification of a cavity which is too narrow.
Tinsdeall and Grimwood (11) investigations into the effectiveness of sound insulation in flat conversions, found problems arising from use of untrained labour.
‘The installation instructions accompanying some propriety floating floors are complex. The contractors used may not be familiar with the installation methods for a particular treatment and often will not understand the acoustic principles of floating floors’.
Common faults found by the researchers where, the bridging of a resilient floor mounting by screwing through a floating floor, failing to leave gaps at the edge of floating floors and screwing ceiling plasterboard through resilient bars directly into the joists.
The results of the survey have shown the constructions tested have increased the sound insulation between flat conversions and that addition of sound insulation is now an important issue to an increasing number of Housing Associations.
5. Conclusions.
The issue of noise pollution in dwellings is an increasing problem. Although noise from neighbours appears to bother only a small proportion of residents in attached dwellings, it is nevertheless the most widespread reported issue of nuisance to Environment Health Officers.
There are significant differences in the likelihood both of hearing noise from neighbours and being bothered by it, as between different types of dwellings. Residents in flats are more than twice as likely to be bothered than residents in semi-detached houses. Unwanted sound is an increasing issue in many buildings. There are no simple solutions for the elimination of noise, as the transmission route is often difficult to clearly define.
Individual tolerance to noise is also different this has been shown in recent cases coming before the courts under the EPA. Property owners and specifies should be aware of the rulings by the House of Lords, could be challenged and future claims may argue a lack of soundproofing breaches their right to privacy under the Human Rights Act 1998.
Sound insulation is more complex than other building effects, due to a number of factors as suggested by McMullan. Timber construction will typically give good insulation against speech, but very poor insulation against a low frequency stereo. A concrete floor is very good at low frequency, but less good at high frequency. At present, sound insulation is virtually the only area of building regulation, which is not tested for workmanship. If sound tests become mandatory, there would be more of an incentive for builders to get it right with the methods of installation in soundproofing. The European Commission has produced a draft directive, which may lead to mandatory testing for noise pollution in buildings. Until this becomes law the building practitioner will walk a tight rope in the case of sound pollution and the Common and Statutory Law.
There is a strong case to insulate against noise both at a social and health level. The installation of systems requires skilled labour to insure trouble free workmanship. The main drawbacks are lack of knowledge by the general public about how noise is transmitted and the cost of noise reducing constructions both in new build and upgrades to existing dwellings.
References:
1. Attenbrough K. 1994. T237, Environmental Control and Public Health, Open University.
2. Department of the Environment, 1998. Digest No 20.
3. Building Research Establishment, September 1997, PD 183/97.
4. Grimwood C. 1995, Complaints in Acoustics, Institute of Acoustics, July/August Bulletin.
5. Insider Housing, October 1999, page 11, CIOH.
6. Insider Housing, Databank Law Update, page 58, June 1999, CIOH.
7. Lbid., p59.
8. Insider Housing, Databank Law Update, page 46, Dec/Jan 2000, CIOH.
9. McMullan R. 1991, page 7, Noise Control in Buildings, BSP Professional Books.
10. Steel C. Research into Acoustic Walling products, unpublished M.Phil. Dissertation, Napier University.
11. Tinsdeall N.J. and Grimwood C.J. 1997, Is the guidance in Approved document E for sound insulation between converted dwellings being following in practice. BRE, PD 183/97.
Tables:
BS 8233: 1999, Sound insulation and noise reduction for buildings-Code of practice.
BRE/CIRIA: 1993, Report 127, Sound control for homes.
DoE, Building Regulations 1995, Approved document E.
Bickerdike Allan Partners, Acoustic Consultants, London.
Anthony Sneider BA (Hons) M.Phil FIMBM MIMgt MCIM
Building Technologist
It has been estimated that up to four million dwellings in the UK have trouble with noisy neighbours. This paper reviews the growing issue of noise pollution in terms of legal provisions in Common and Statutory Law.
Noise pollution can be described as a health hazard, both in the workplace and at home, yet the law in terms of Health and safety only applies to the workplace. This paper examines the issues of noise pollution in today’s buildings, from the perspective of a building practitioner. In discussing the issue of noise and its pollution in buildings, the topics that will be addressed are, why we need to insulate against noise? How sound insulation is described? What physical characteristics contribute to sound insulation? This paper will review the growing issue of noise pollution in terms of recent legal provisions for noise pollution in Common and Statutory Law, and the importance of quality of detailing/workmanship in the installation of acoustic systems.
1. Introduction
The definition of noise can be rather subjective, but when looking to minimise noise transmission from one space to another, this noise can be defined as sound, which is undesired by the occupants. However, it should be noted that individuals vary widely in their sensitivity and tolerance to noise. There are minimum pressures, which the average individual can detect and the maximum pressures, which can be tolerated before damage occurs to an individuals health or well being. Hearing damage leading to deafness also depends on energy rather than loudness. A tenfold increase in energy can increase the risk of hearing damage by ten but will only sound twice as loud. Once hearing is lost it can not be regained, hence the Health and Safety requirements in the workplace.
Research into the issue of noise pollution, has found that this type of building defect out ranks other building defects, such as comfort, dampness, condensation, thermal insulation and heating. 1 in 5 families are troubled with noise pollution (1). Recent findings by Department of the Environment, in the Digest of Environmental Statistics No. 20 1998 (2), have shown the level of complaints of noise is increasing. In addition, a sound insulation survey was carried out by the Building Research Establishment (3), in which the DoE asked the BRE to measure the sound insulation of flat conversions and the effectiveness of the Building Regulations. The report results of the survey suggested that, overall, the constructions tested have increased the sound insulation between flat conversions. In addition sound insulation is now an important issue to an increasing number of Housing Associations. Grimwood (4) has also found noise sources, especially, domestic sound reproduction equipment to be problematic and this equipment is becoming more powerful.
In a domestic situation, issues with noisy neighbours can be very significant for adjoining properties, whether this is multiple occupancy flats or houses. It has been estimated that up to four million dwellings in the UK have problems with noisy neighbours. The House of Lords have recent ruling has provided some comfort to property owners regarding the improvement of dwellings regards to noise issues, but the issue of soundproofing still remains.
People tend to associate noise with inconsiderate neighbours, not with the construction of the dwelling itself. However, if dwellings were built to proper building standards, neighbours should not be heard, therefore, the need to insulate against unwanted noise.
2. Why do we need to insulate against noise?
Exposure to high levels of noise can be dangerous and awareness to the potential dangers is required. The human ear notices high frequencies more easily than low frequencies. This characteristic has been incorporated into sound-level meters using the A-weighting network. A-weighted sound-pressure levels can be measured directly on a sound-level meter.
Sound-pressure levels are not combined by simply adding together the decibel values. A conversational voice at 1-m distance results in a sound-pressure level of about 57 to 62 dBA. Two voices together would not cause a level of 130 dB; that would be louder than a pneumatic drill. The following tables describe the changes in sound level and the effect on loudness.
|
Changes in sound level
|
Change in loudness
|
|
+/- 1dB
|
Barely Perceivable
|
|
+/- 3dB
|
Requires close attention to notice
|
|
+/- 5dB
|
Quite noticeable
|
|
+/- 10dB
|
Dramatic: nearly twice as loud
|
|
+/- 20dB
|
Striking: fourfold change
|
Maximum steady noise levels for reliable speech communication.
|
Distance between
talker and listener m |
Noise level
dBA |
||
|
Normal voice
|
Raised voice
|
||
|
1
|
57
|
62
|
|
|
2
|
51
|
56
|
|
|
4
|
45
|
50
|
|
|
8
|
39
|
44
|
|
Prolonged exposure to high noise levels will induce hearing loss. It is for this reason that Health and Safety at work Act requires noise levels in a work place to be limited to less than 90 dB (A) during an 8-hour working day. At a noise level of 105 dB (A), exposure time is limited by the Act to 15 minutes. The following tables describe the range of sound pressure of typical every day noise levels and the way individuals perceive them.
|
Changes in sound level
|
|
|
140
|
Threshold of pain
|
|
120
|
Aircraft taking off (at 25 m)
|
|
110
|
Pneumatic drill
|
|
100
|
Noisy factory
|
|
90
|
Inside underground
|
|
80
|
Inside bus
|
|
70
|
Average traffic on main road (at kerb)
|
|
60
|
Normal conversation (at 1 m)
|
|
50
|
Typical office
|
|
40
|
Living room in suburban area
|
|
30
|
Library
|
|
20
|
Bedroom at night
|
|
10
|
Insulated broadcasting studio
|
|
0
|
Threshold of hearing
|
|
Levels of Noise
|
|
|
Intolerable
|
120 to 140 dB
|
|
Very Noisy
|
85 to 120 dB
|
|
Noisy
|
55 to 90 dB
|
|
Quiet
|
30 to 55 dB
|
|
Very Quiet
|
0 to 30 dB
|
In the home noise individuals produce can vary dependent on the activity being undertaken, for example vacuum the carpets, washing machine, television, music and now home entertainment systems, which produce noise between rooms can be a nuisance and with modern sound systems the energy output has increased dramatically. The hearing of noise and the fact of being bothered by neighbour’s noise are the key issues that lawyers and courts are dealing with.
Although not a statutory requirement, it is recommended for example, internal walls between bedrooms and toilets or bathrooms should have a minimum noise reduction value of 38 dB. The National House Building Council requirements call for acoustic insulation between bathrooms, toilets and habitable rooms. This action was to reduce the number of complaints from owners regarding the filling of water closets, shower’s etc.
Unfortunately, building design and legislation has failed to keep pace with changing life styles and the demand for privacy, peace and quiet. In statutory law noise is a statutory nuisance under the provisions of the Environmental Protection Act 1990 (EPA). In England and Wales, a local authority’s power comes from Section 80 of EPA. In Scotland the Control of Pollution Act 1974 section 58 and Northern Ireland the Pollution Control and Local Government Act describes the steps, which local authorities are to take, where they are satisfied that a noise nuisance exists.
The main principles established under these Acts are as follows.
a) There is no prescribed level above which a noise becomes a statutory nuisance. Each case is considered on its merits and account taken of the likely reaction of a reasonable person. The noise complained of need not be injurious to health; the criterion can be one of interfering with ordinary comfort or amenity.
b) Where the noisemaker is operating from industrial, trade or business premises, it is a defence to show that the best practicable means to control noise has been used.
In Common law, civil action can be taken against noise nuisance and each case is assessed on its merits. The criterion for civil action is how the noise affects the individual compared with the ordinary inconvenience suffered by the public at large.
Section 80 of the EPA Act 1990, enables the complainant to bring proceedings in the magistrate’s court. Recent actions by Budd v Colchester BC, Mills v Southwark and Baxter v Camden and Pettigrew v Inverclyde Council, have added to the debate on statutory law.
In the case of Budd v Colchester BC (5), the Court of Appeal considered the detail required in an abatement notice on the appellant under section 80 of the EPA 1990. Mr Budd kept six greyhounds at his house, his neighbours complained to the local authority about the dogs barking, particularly in the early hours of the morning.
The House of Lords have considered the case of Mills v Southwark LBC (6) and Baxter v Camden LBC (7). (A common problem between these cases is the everyday noises of neighbours). The case’s centred on the issue of sound proofing in the tenant’s flats or, rather the lack of it.
In the case of Pettigrew v Inverclyde Council (8), a local authority tenant and her two children raised summary applications under section 82 of the EPA, against her landlord and the owner of the property above her. The plaintive was seeking the court to find and declare that a statutory nuisance in terms of the Act existed. The court to make an order against the first and/or second defender to abate the nuisance by provision of adequate sound insulation in the respective subjects owned by them or in the common parts between the properties.
The common issue here is that of inadequate sound proofing between the dwellings. The arguments where based on the fact that the building satisfied building requirements at the time of construction. The occupiers where unhappy with the level of sound being transmitted into their dwellings.
3. How is sound insulation described?
Sound insulation can be described in a variety of ways. The three main situations are, room-to room sound insulation (source is within the building), Impact sound insulation (source is footsteps or other impacts on the building structure) and Outside-to-inside sound insulation (source is in the open air).
The method for the measurement of sound insulation is laid down in BS 2750.
The problem arises with the nature of sound its self. In the case of a floor this can be identified as impact related and airborne sound. Combating this sound transmission requires two forms of acoustic action, which operate in distinct ways – sound insulation and sound absorption.
British Standard 8233: 1999, Sound insulation and noise reduction for buildings, sets out the recommendations for the control of noise in and around buildings and suggests appropriate criteria and limits for different situations.
The Building Regulations 1995, Approved Document E (DoE and Welsh Office) and Scottish Building Regulations Part H, deal with the requirement to protect occupants of a dwelling from excessive noise transmitted from other parts of a building.
|
Current Requirements.
|
|
|
Type of tests and partition
|
Single figure value
|
|
Airborne sound for walls
|
Not less than 53dB
|
|
Airborne sound for floors
|
Not less than 52dB
|
|
Impact sound for floors
|
Not greater than 61dB
|
Sound insulation levels of a building can be tested and figures given for each construction element, such as floors, internal party and external walls.
3.1 Room-to-room airborne sound insulation.
Voices, television sets, hi-fi and musical instruments are all sources of airborne sound. The airborne sound insulation between two rooms can be measured by generating a steady, broad-band sound level in one room (the source room) and measuring the sound-pressure level in both the source and receiving rooms over a range of frequencies.
3.2 Impact sound insulation.
The impact insulation of a floor and its surrounding construction can be tested. The construction is excited by a standardised impact sound source (a tapping machine) and the resulting sound level is measured in the receiving room.
3.3 Out-to-inside sound insulation.
The sound insulation of a building facade can be tested using either road traffic or a loudspeaker as the source of noise.
Now we have discussed the main areas in which sound insulation is required to be addressed in terms of improving the construction of dwellings. We require investigating the physical characteristics that contribute to sound insulation.
4. What physical characteristics contribute to sound insulation?
It is important not to confuse the terms Insulation and Absorption. An absorber such as fibrous quilt will not itself provide much sound insulation, because it has a Low Mass and is permeable to air. Consequently, it is not a suitable material to fill up an aperture through a masonry partition if optimum sound insulation is required. Absorbers can contribute to good sound insulation is installed in the cavity between leaves in double-leaf partitions, where they improve the acoustic isolation between the two leaves (Mass-spring-Mass).
Sound insulation is the main method of controlling the movement of sound within buildings. McMullan (9) in his book on Noise control in buildings identifies the common problems of noise in buildings and gives practical solutions to these problems of unwanted sound.
• Mass.
• Isolation.
• Mass-air resonance.
• Control of flanking transmission.
• Quality of detailing and workmanship.
• Absorption.
4.1 Mass.
The sound insulation of any single-leaf or floor built without gaps depends mainly on its MASS. According to MASS LAW, there will be an increase in sound insulation of about 5dB if the mass per unit area is doubled. In addition, each time the frequency is doubled, a 6dB increase will occur.
For example, the average sound reduction of a brick wall increases from 45 dB to 50 dB when the thickness is doubled.
The critical frequency of a one-brick wall occurs at about 100Hz, and of a half-brick wall at about 200 Hz. The sound insulation of the latter is poorer, not only, because the MASS is reduced, but also because the critical frequency is at a point where its effect is more serious.
Traditionally, construction methods have believed it necessary to incorporate a heavy material into the building fabric in order to achieve a high level of sound absorption to resist the sound energy attempting to pass through it. Doubling the mass of a structure or partition normally reduces the sound transmission by one quarter or 6 dB.
4.2 Isolation.
In principle, double-leaf constructed walls can give better sound insulation than single-leaf wall in part due to MASS, but also due to the way the sound waves encounter two separate masses, whose sound insulation can be added together. In practice, this can occur only if the two masses were completely ISOLATED from one another. In lightweight forms of domestic construction owe much of their sound-insulation performance to isolation.
In resent research by Steel (10), found in developing new light weight acoustic walling products, that the factors effecting performance where;
• Additional mass.
• Stiffness/ Rigidity.
• Separation/ Isolation.
• Completeness/ Airtight.
• Depth of Cavities.
This practical research in an acoustic laboratory has shown the mass-spring-mass theory at work and how sound absorbent materials interact in the construction of acoustic walling. When sound waves come into contact with n absorbent material it enters the material and the energy of the wave is dissipated as small quantities of heat. This is because rather than force the quilt into vibration and form a wave on the opposite side. The fibres within the quilt will move against each other causing friction within the quilt. This action changes the wave (sound) energy into heat energy, weakening the force of the wave and thereby reducing transmission.
4.3 Control of flanking transmission.
The sound insulation between two spaces depends not only on the sound transmitted through the intervening wall or floor, but also on FLANKING TRANSMISSON. This sound travels along any elements common to both rooms.
If flanking constructions are not correctly specified, flanking transmission can equal or even exceed direct transmission and degrade the overall result. Flanking transmission is a complex matter, not only is the construction and size of the flanking element significant, but also is any interaction between it and the wall or floor. The specification of a sound-insulating wall or floor is incomplete if not accompanied by an appropriate flanking construction specification.
4.4 Quality of detailing and workmanship.
A wall or floor will give its expected sound insulation only if it and the surrounding construction are built without faults. Some possible faults are:
• Areas of low sound insulation; for example, gaps or holes in the wall or floor, areas of Low Mass.
• Mechanical bridging of isolation; for example, unwanted-ridged connections such as nails through floating floors or the selection of incorrect wall ties in the cavity.
• Acoustic coupling between the leaves of a double-leaf partition; for example, omission of a specified absorbent quilt or the specification of a cavity which is too narrow.
Tinsdeall and Grimwood (11) investigations into the effectiveness of sound insulation in flat conversions, found problems arising from use of untrained labour.
‘The installation instructions accompanying some propriety floating floors are complex. The contractors used may not be familiar with the installation methods for a particular treatment and often will not understand the acoustic principles of floating floors’.
Common faults found by the researchers where, the bridging of a resilient floor mounting by screwing through a floating floor, failing to leave gaps at the edge of floating floors and screwing ceiling plasterboard through resilient bars directly into the joists.
The results of the survey have shown the constructions tested have increased the sound insulation between flat conversions and that addition of sound insulation is now an important issue to an increasing number of Housing Associations.
5. Conclusions.
The issue of noise pollution in dwellings is an increasing problem. Although noise from neighbours appears to bother only a small proportion of residents in attached dwellings, it is nevertheless the most widespread reported issue of nuisance to Environment Health Officers.
There are significant differences in the likelihood both of hearing noise from neighbours and being bothered by it, as between different types of dwellings. Residents in flats are more than twice as likely to be bothered than residents in semi-detached houses. Unwanted sound is an increasing issue in many buildings. There are no simple solutions for the elimination of noise, as the transmission route is often difficult to clearly define.
Individual tolerance to noise is also different this has been shown in recent cases coming before the courts under the EPA. Property owners and specifies should be aware of the rulings by the House of Lords, could be challenged and future claims may argue a lack of soundproofing breaches their right to privacy under the Human Rights Act 1998.
Sound insulation is more complex than other building effects, due to a number of factors as suggested by McMullan. Timber construction will typically give good insulation against speech, but very poor insulation against a low frequency stereo. A concrete floor is very good at low frequency, but less good at high frequency. At present, sound insulation is virtually the only area of building regulation, which is not tested for workmanship. If sound tests become mandatory, there would be more of an incentive for builders to get it right with the methods of installation in soundproofing. The European Commission has produced a draft directive, which may lead to mandatory testing for noise pollution in buildings. Until this becomes law the building practitioner will walk a tight rope in the case of sound pollution and the Common and Statutory Law.
There is a strong case to insulate against noise both at a social and health level. The installation of systems requires skilled labour to insure trouble free workmanship. The main drawbacks are lack of knowledge by the general public about how noise is transmitted and the cost of noise reducing constructions both in new build and upgrades to existing dwellings.
References:
1. Attenbrough K. 1994. T237, Environmental Control and Public Health, Open University.
2. Department of the Environment, 1998. Digest No 20.
3. Building Research Establishment, September 1997, PD 183/97.
4. Grimwood C. 1995, Complaints in Acoustics, Institute of Acoustics, July/August Bulletin.
5. Insider Housing, October 1999, page 11, CIOH.
6. Insider Housing, Databank Law Update, page 58, June 1999, CIOH.
7. Lbid., p59.
8. Insider Housing, Databank Law Update, page 46, Dec/Jan 2000, CIOH.
9. McMullan R. 1991, page 7, Noise Control in Buildings, BSP Professional Books.
10. Steel C. Research into Acoustic Walling products, unpublished M.Phil. Dissertation, Napier University.
11. Tinsdeall N.J. and Grimwood C.J. 1997, Is the guidance in Approved document E for sound insulation between converted dwellings being following in practice. BRE, PD 183/97.
Tables:
BS 8233: 1999, Sound insulation and noise reduction for buildings-Code of practice.
BRE/CIRIA: 1993, Report 127, Sound control for homes.
DoE, Building Regulations 1995, Approved document E.
Bickerdike Allan Partners, Acoustic Consultants, London.
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