C Max Absorb at Ellerslie School
At Ellerslie School in Auckland, DLM Architects designed two new ILE classroom blocks. T&R designed, installed and tested the inclusion of C Max Absorb suspended ceiling tiles. The results were truly impressive.
Children are inefficient listeners who require optimal acoustic conditions in order to hear and understand (Valentine, Halstead, McGunnigle, Dodd, Hellier, Wood & Simpson, 2002). They are neurologically undeveloped and lack experience to predict from context, especially younger students who are only starting to grasp the basics of comprehension. Children who miss key words, phrases and concepts because of poor listening conditions may do poorly academically and suffer from behavioural problems.
Recently, new classrooms are being designed as open-plan environments where several class-bases share the same space, (resulting in a large number of children in one larger area). These Innovative Learning Environments (ILE) are emerging to facilitate group work and benefit the children’s social development; promoting the sharing of skills, ideas and experiences.
However, many acoustic issues arise with ILE, such as high noise levels coming from other class-bases in the same space. Acoustic conditions often do not facilitate a good Signal to Noise Ratio, especially further away from the teacher. Furthermore, the larger spatial volumes lead to higher Reverberation Times which negatively affect Speech Intelligibility. Longer Reverberation Times also exacerbate background noise. AS/NZS 2107 recommends a Reverberation Time of 0.4 - 0.5 seconds.
Designing an optimal acoustic environment prevents unsatisfactory acoustics affecting the listening capabilities of children at school. It’s not only students that suffer from sub-optimal acoustics either; loud or reverberant classrooms may cause teachers to raise their voices, leading to increased stress, fatigue and potential voice impairment and nodules on vocal chords.
At Ellerslie School in Auckland, DLM Architects designed two new ILE classroom blocks. Their design included Autex Composition coverage on all the walls, carpet tiles on the floor and direct fix acoustic panels on the pitched cathedral style ceiling. However, due to budget constraints, DLM Architects were instructed to remove the acoustic ceiling panels contrary to their recommendations. The ceiling was always having a pasterboard sub-lining for bracing so this then became the actual lining.
Once the classrooms were completed in April and June 2015, DLM Architects received complaints from teachers and the principal of the school relating to the acoustics in these new spaces. Testing confirmed that the Reverberation well exceeded the recommended times. One classroom had an average Reverberation Time of 1.06 seconds whereas the other tested at 0.80 seconds.
Reverberation times above 1 second are incredibly detrimental to speech intelligibility.
It was agreed to retrofit the ceiling at a later stage when funding became available. Over the school holiday period, the classrooms were retrofitted with a T&R Interior Systems C Max Absorb 15mm suspended ceiling with an NRC of 0.95. Consequent retesting confirmed that this was essential to bring the Reverberation Time to acceptable levels. The same classrooms now had a reverberation time of 0.45 and 0.42 seconds unoccupied.
This highlights that in ILE, the acoustic properties must be integral to the whole design; due to the larger volumes and low Reverberation time required. It is not sufficient to merely treat a few surfaces. However, even though DLM Architects had correctly addressed the acoustics during the design phase, acoustic treatments are often sacrificed when the budget gets tight as in the Ellerslie School project. Ironically, retrofitting acoustic treatment into a room that is “unfit for purpose” ends up costing the client (Ministry of Education) considerably more.
Specific criteria for acoustic-measurements in classrooms are currently not included in the New Zealand Building Code, and this responsibility falls with architects and designers. However, guidelines for acoustics in Education spaces can be found in AS/NZS 2107. The New Zealand Ministry of Education encourages schools to ensure that acoustic conditions in teaching spaces provide the best possible outcome and strongly recommend that schools remedy any acoustic shortcomings.