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Classrooms soundproof against rain and each other

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article image A layer of Wavebar, doubled above each dividing wall in the roof cavity, has insulated classrooms from each other and from the noise of heavy rain.

According to Pyrotek Soundguard , teachers at New Zealand's Randwick Park Primary School can now address their classes without shouting, thanks to a two-pronged soundproofing strategy using Soundguard materials to shut out the noise of heavy rain.

The outcome of the noise control measures proves that providing a quiet environment -certainly for students but equally for office workers, venue users and the public at large - ranks up with climate control and ergonomics for improving the human experience and performance.

"The original design of the classrooms did not fully consider how much noise heavy rain can make through an untreated roofing system. Or fully consider noise migrating between classrooms," says Soundguard's Philip Cadwallen.

"The design shortfalls meant that teachers and students in one classroom could easily hear what was happening next door. This made it very hard for the young students to concentrate and the teacher to teach.

"Actually, noise between classrooms was only a problem when it wasn't raining, because if it was, the teachers and students could hear nothing but the drumming of raindrops on the steel roofing!"

The soundproofing strategy - which involved extensive use of Wavebar, Soundguard's flexible barium-loaded vinyl - was developed by engineering consultants, Norman Disney & Young with inputs from architectural firm, Maunsell and from Soundguard.

"To stop transmission between classrooms, the consultants called for a Wavebar barrier between the ceiling and the roofing iron in the roof cavity. The ceiling in the classrooms consists of a corrugated perforated panel, designed only to reduce reverberation within the rooms.

“Above the panels was a 50 mm thick glass fibre blanket with a commonly used roofing iron. Above the internal dividing wall between the classrooms was an open pathway where noise could travel through the ceiling tiles, through the cavity and down through the neighbouring classrooms' ceiling, helped along by reflections off the underside of the roofing iron," Philip Cadwallen explains.

"A double layer of 8 kg/m² Wavebar was to be installed directly above each dividing wall in the roof cavity, effectively blocking the transmission path of noise between the rooms."

A single layer of this weight of Wavebar boasts an Rw of 30 and a ceiling attenuation class (CAC) of 50 with standard ceiling tiles.

"All the Wavebar in the ceiling cavity was fully sealed using a flexible mastic sealant to provide completely airtight seals between flashings, purlins and the roofing iron above," says Philip Cadwallen.

"To counter the rain noise, 8kg/m² Wavebar was laid down as a 'blanket' beneath the roofing iron and above the purlins, creating a complete barrier against noise transmission.

"Soundguard supplied the Wavebar in more manageable custom-cut rolls. This also reduced installation labour and wastage.

"Instead of butting the edges together and leaving 'leaks' for the noise to travel through, all of the joints were over-lapped at least 50 mm, so creating a continuous acoustic barrier from the outer edges of the external walls across the entire roof area," Philip Cadwallen concludes.

Testimony to the efficacy of the work comes from the school's Room 10 teacher, who reports: "We noticed an immediate difference. It has provided a very peaceful atmosphere. It's not until you step outside that you realise it's actually raining. After one over-excited class session, I went to apologise to the teacher next door for disturbing his lessons. He replied that he didn't even notice it."

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