We are delighted that Acoustics of Schools: a design guide has finally been published. As well as making a significant contribution to the content, Jack Harvie-Clark has coordinated the publication of the document; some people will notice that all the schools featured on the front cover had the acoustic design provided by Apex Acoustics. The IOA and ANC agreed to jointly fund the cost of professional designers; all the content, however, was produced on a voluntary basis by the committee mentioned in the inside front cover. You can download the document from the IOA or ANC websites, or the link below.
From the initial concept of a light-touch review, updating references and filling gaps where previously there was no guidance, the final document is actually more detailed, with new chapters being introduced to expand on previous guidance and to introduce new information where previously there was none.
Below is a summary of the content of the new design guide, with a reminder about pre-existing content and highlighting significant elements of new material. Suggestions for improvements are welcome. It is hoped that additional practise notes and example calculations will be added to the available information, to facilitate the design and construction of schools that perform well acoustically. Please contact either Jack Harvie-Clark or the ANC if you have any suggestions for improvements.
Summary of the contents
Section 1 contains an overview of the legislative requirements to consider the acoustics of schools, and a summary of the changes to the performance standards that are in BB 93: 2014.
Section 2 considers environmental noise impacts on a school site, and suggests how the design may respond to such impacts. Preferred noise limits for external activities and teaching are described, and different natural ventilation strategies to control external noise ingress are discussed. There is new information on noise from equipment in teaching and learning spaces; these limits are suggested for compliance with the School Premises Regulations and Independent Schools Standards. Different limits are proposed for different categories of equipment. Methods for calculating noise from equipment are considered in the new Appendix 5.
Section 3 describes the assessment of internal sound insulation, and the specification of appropriate element performances to meet the standards in BB 93. Construction details have been added to the diagrams for in-situ concrete floors on metal decks, as this has been a common construction approach. Currently Apex are seeing more school designs with pre-cast concrete planks, exposed soffits (for thermal mass), and a screed on top, which can perform very well acoustically. There is a clarification on the application of sound insulation between circulation areas, classrooms and non-teaching rooms. Apex considers that further guidance on the classification of ventilation systems is necessary, for consistency between competing contractors; it was not possible to include this in the design guide due to time constraints.
Section 4 describes the design of rooms for speech. Consideration for open plan areas has been removed and is dealt with in much greater detail in the new Section 7. Section 5 concerns the design of rooms for music; this has been updated in line with the government’s separate recent guidance on music accommodation in schools. Section 6 has been more substantially revised, as have the performance standards for rooms designed for pupils with special hearing and communication needs.
Section 7 is entirely new, devoted to the design of open plan spaces. There is much more experience and information available on this subject than available previously, and the performance standards for open plan spaces have been extended in BB 93: 2014. Different types of open plan accommodation are described, and an activity management risk chart enables a non-acoustician to assess the acoustic risk of open plan designs. This is anticipated to be a useful tool to highlight the level of acoustic risk before any acoustic modelling takes place. Acoustic modelling is described in the new Appendix 6.
Section 8 is also brand new, and addresses issues for refurbishments and for integrated design. Performance standards for refurbishments are now included in BB 93: 2014, along with a description of where these standards apply. The notes on integrated design seek to remind acoustic designers of the other environmental and building fabric considerations that the architect must balance. It is easy to forget that buildings must also perform in terms of daylighting, air quality, thermal comfort, structural integrity, robustness, layout and of course aesthetics, for example.
Appendices 1 to 3 have been retained and updated to describe the performance parameters used in BB 93: 2014. The calculation of the mid-frequency reverberation time, Tmf,max from the third octave measurements is described, as is the in-situ measurements of airborne and impact sound insulation, Dw and L’w. It will be interesting to see how often these are used in practice, and whether consultants routinely calculate both parameters in case one of them demonstrates a pass. If you have heard Jack talk on the subject, you will know that he is not a proponent of using in-situ performance parameters, for many reasons.
Appendix 4 is a new section; it describes the calculation method for absorption in sports halls, swimming pools, gymnasia, dance studios and other normally unfurnished activity spaces. BB 93: 2014 refers to this method as a means of compliance with the absorption requirements in these spaces without the need to undertake reverberation time measurements. This is one of the most significant additions to the guidance, and it will be interesting to see how well it works in practice.
Appendix 5 is another new section, and describes the calculation of noise from equipment. It is a summary of standards that may be appropriate to adopt in different circumstances, for both new and legacy equipment. Any feedback on this section would also be welcome.
Appendix 6 describes the acoustic modelling of open plan spaces. Guidance on this subject was previously issued in a note that followed BB 93: 2004, and much additional information and clarifications have been included. In particular, spectra for normal and raised voice effort are identified, and the octave band weighting factors for the calculation of STI, as these differ from the spectra used in the ISO standard for assessing STI from public address systems. These are the spectra used in ISO 3382-3 for open plan office assessments – and ISO 3382-3 actually refers to the previous BB 93 computer modelling document as one of the sources of these spectra.
Appendix 7 describes the assessment of noise from window actuators, responding to the new performance criterion in BB 93: 2014. The appropriate use of the ISO 16032 is described for measurements. The assessment of measurements from a suitable reference installation is also described, to enable actuator manufacturers to qualify their products without needing to test every possible combination of window frame material, opening light dimensions, glass type, and fixing details, for example. The possible effect of these variables must nonetheless be considered. It will be interesting to see how this is adopted in practice.
Read more about our research of acoustics in schools here.