Glass cover with high acoustic performance and specification chal- lenges Milena Lima Atenua Som São Paulo, São Paulo, Brazil

ABSTRACT

We are faced with a situation in which a commercial establishment in a residential area re- ceives constant complaints due to the loud sound of music, the request was made with a high degree of urgency, the challenge of this study is to find an acoustic solution that maintains the requested aesthetics, bringing a comfortable atmosphere to those who are inside the environment and remedy the apprehension of the neighborhood. After a thorough field study and technical measurements, it was defined that the insulation required for making the roof will be Rw50.

1. INTRODUCTION

The biggest challenge was to find reliable tests, already carried out on high-performance glass that would guarantee the acoustic efficiency required. This proved to be a difficulty because not enough data were found and the deadline for execution was extremely short. The acoustic tests were started using Brüel & Kjær equipment, a model 2270-S sound level meter, Capacitive Microphone 4189 and Preamplifier ZC-0032 in a laboratory meeting the recommendations of ISO 717-1:2013 Rating of sound insulation in buildings and of building elements - Part 1: Airborne sound insulation, ISO 16283-1:2014 Acoustics – Field measurement of sound insulation in buildings and of building ele- ments - Part 1: Airborne sound insulation and ISO 3382- 2:2008 Acoustics — Measurement of room acoustic parameters — Part 2: Reverberation time in current ordinary rooms. During the laboratory tests, several tests were necessary to achieve the expected result, with the data available in Brazilian regarding the loss of sound transmission from the glasses, we calculated a specification that theoret- ically would meet the need, but the results obtained were very different, requiring some modifications beyond the glass, until make the final product.

2. First Steps

The first step to start manufacturing the project was based on the studies we had in hand to assemble a glass composition that theoretically would meet the requested needs, but there was no

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content to prove its effectiveness. That's why it was extremely important that the tests were done even before the material started to be made in the factory.

An initial join was made in which the necessary result was not achieved, as shown in the image below:

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Figure 1: First Test

As the initial composition did not reach the required performance, a more advanced study on glass composition was necessary, as there was not much time for many tests due to the short delivery time.

The lack of this type of content available in Brazil was really a hindrance, because in the end we had to make an estimate with our knowledge for soon after starting other tests. It could have assumed that some glass on the market would already deliver the result of Rw 50, but there was also a limitation in budget and waiting time.

2.2. Test

The measurements of the sound insulation of the sample were carried out in test chambers developed exclusively for this purpose. The test chambers were designed to generate the best possible conditions to meet the requirements of ISO 140-4:1998 (engineering method), generating results comparable to tests carried out in accordance with ISO 140-3:1995 - “Acoustics Measurement of

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sound insulation in buildings and of building elements Part 3: Laboratory measurements of airborne sound insulation of building elements”, but with lower precision.

Acoustic signal type: White noise. Source positions for equivalent level measurements: 2 po- sitions at the corners of the emission chamber. Measuring points: 5 points in each chamber. Number of records of equivalent levels in each chamber: 10 records + background noise record at one point (receiving chamber). Minimum measurement period: 12 seconds. Minimum background noise meas- urement period: 60 seconds. Reverberation time measurement points: 3 points. Number of decays at each point: 3 decays.

3. Final Results

It was necessary to modify the initial concepts to achieve the result. Firstly, we would not be using only a composition of glasses, there was a need to join some spacings as well. A structure was assembled with three glasses of different thicknesses, an air chamber and an aluminum profile ap- proximately 100mm thick.

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Figure 2: Final results 4. CONCLUSIONS

Not having a study that proves the efficiency of a product should not somehow become an impediment to its realization. If there is the possibility of verifying the facts and a good base, this will facilitate the process, generating the possibility of many other things to be created.

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6. REFERENCES

1. MARCO, Conrado Silva de. Elementos de Acústica Arquitetônica – NOBEL. 2. ABNT NBR 15575-1:2013 Edificações habitacionais - Desempenho Parte 1: Requisitos

Gerais. 3. ABNT NBR 15575-4:2013 Edificações habitacionais - Desempenho Parte 4: Requisitos

para os sistemas de vedações verticais internas e externas SVVIE. 4. ABNT NBR 10151: 2000 Versão Corrigida: 2003 (em revisão) Acústica - Avaliação do

ruído em áreas habitadas, visando o conforto da comunidade – Procedimento. 5. ABNT NBR 16313:2014 Acústica – Terminologia. 6. ISO 717-1:2013 Acoustics - Rating of sound insulation in buildings and of building

elements - Part 1: Airborne sound insulation. 7. ISO 16283-1:2014 Acoustics – Field measurement of sound insulation in buildings and of

buildings elements – Part 1: Airbone sound insulation.

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