The importance of efficient systems
Public buildings have very specific acoustic requirements within certain rooms, often determined by the activity within the room which in turn sets the acoustic performance specification. School and hospital environments are a prime example of where effective acoustic solutions are essential, demanding a calm and comfortable environment for all. Noise can seriously harm an individual’s health leading to pain, fatigue, hearing impairment and communication problems, as well as interfering with daily activities and performance at school. Indeed, high-quality acoustics in the classroom for example, are necessary for all children to be able to learn, and for deaf and hard-of-hearing children they are vital.
Legislation specifically dictates the acoustic performance required in public buildings such as those providing rooms for residential purposes (Approved Document E of the Building Regulations) and for specific sectors such as Education (BB93) and Healthcare (HTM 08-01). But whilst there is no specific legislation relating to other busy public areas and offices, these areas also demand a reduction in noise pollution, where the building’s occupants require an environment which is conducive to their well-being, comfort and efficiency.
Testing in schools
Under the Building Schools for the Future (BSF) programme, the Government has set out plans to make mandatory acoustic testing for all new schools built. This follows recent reports that only 21% of those local authorities that responded to a recent call for information, had new schools with acoustic performance that complies with the requirements set out in Building Bulletin 93 – the government guidance for meeting Part E of the Building Regulations.
Under the new measures local authorities that have already constructed schools with BSF funding may also need to provide proof that the most recent school complies with acoustic standards before further funding is released. This certainly demonstrates the importance now attached to good acoustics within the learning environment and will undoubtedly focus the minds of architects, designers and building engineers currently working on BSF projects.
Building Regulations 2000: Approved Document E4: 2000 (2003) covers the requirements for sound insulation, reverberation time and indoor ambient noise levels. It states that ‘Each room or other space in a school building shall be designed and constructed in such a way that it has the acoustic conditions and the insulation against disturbance by noise appropriate to its intended use’.
In addition, the Department of Children, Schools and Families (DCSF’s) Building Bulletin 93 sets out to provide a regulatory framework for the acoustic design of schools in support of the Building Regulations. Areas covered include background noise, noise transfer between rooms and reverberation times i.e. the amount of time it takes for a sound to die away.
It covers elements such as airborne sound transmission from circulation spaces e.g. corridors and stairwells; impact sound e.g. footsteps transmitted into spaces via floors; and reverberation times in teaching and study spaces, with requirements to provide suitable performance to allow clear communication of speech between teacher and pupil and between groups of pupils in teaching and study spaces.
There is also specific guidance in relation to different areas, dependent on their classification in terms of activity noise and noise tolerance. For example, a music recital room has very high activity noise (as the ‘source room’) but also very low noise tolerance (as the ‘receiving room’) meaning there are specific performance requirements to their construction – illustrated in table 1.
The activity noise and noise tolerances of different areas is also very important to consider in the planning of other public buildings such as health buildings. Specific guidance can be sought from the Health Technical Memorandum (HTM), which sets out the performance criteria for hospitals. HTM 56 offers direction on the design and specification of partitions that will meet the general requirements of users and conditions of use in health buildings and table 2 displays the airbourne sound insulation requirements for most of the common activity spaces within a typical hospital from HTM 56.
However, HTM 2045: Acoustics will eventually replace the acoustic requirements set out in HTM 56, and is concerned with the design considerations and in particular the control, reduction and absorption of noise (and vibration) in hospitals. The general principals are that internal environments must be protected from external noise sources, noise from internal areas should not adversely intrude on other internal areas and internally generated noise should not adversely affect the external environment.
The demanding conditions within public buildings certainly call for sophisticated acoustic solutions equipped to meeting all the requirements and legislation. One such solution to achieve acoustic performance is to use mineral wool insulation, which has excellent acoustic absorption characteristics, making it ideal for use in a public building environment and it can be used to significantly improve the acoustic performance of plasterboard partitions. Its use in carefully specified constructions with good detailing contributes significantly towards the requirements stipulated in Approved Document E.
In an unfilled floor cavity, for example, the floor deck, plasterboard and cavity alone must provide the sound insulation, which can result in a hollow sounding floor. Adding mineral wool improves the sound insulation by dissipating the sound energy as heat, due to the friction between the vibrating air molecules and strands in the narrow air paths within the mineral wool.
Fit for purpose
Different systems are available to ensure applications are fit for purpose and cost effective. Within a school building for example, for those areas that are required to achieve a sound reduction performance of at least 40dBRw, such as a science laboratory, 12.5mm Knauf Wallboard each side of 50mm Knauf Insulation Acoustic Partition Roll with 50 or 70mm metal C studs will meet the requirements.
When it comes to the much higher stipulation for music rooms (60dBRw), 2 x 15mm Knauf Soundshield each side of 50mm Knauf Insulation Acoustic Partition Roll with staggered 92mm metal studs is advised. However, such a construction can only achieve its expected performance if the junction details are also carefully designed and correctly installed.
Mineral wool insulation incorporated into roofs, walls and floors can make a significant contribution to the acoustic performance of a building. Built up metal roofs for instance, are able to provide a high level of separation between the two sides of the roof. With the inclusion of mineral wool insulation, high levels of sound absorption are possible, ensuring that issues caused by rain noise are also minimised.
With mandatory testing on the cards for schools in particular, it seems that good acoustic design has quickly moved up the agenda meaning architects, designers and building engineers must now see its inclusion as integral to any new public building design.