Experimental investigation of the effect of moisture on the acoustic properties of lightweight substrates used in green envelopes

Attal, Emmanuel; l'Epine, Yorick Buot de; Dauchez, Nicolas; Dubus, Bertrand

doi:10.1016/j.apacoust.2021.108108

Cited by 10 publications

(4 citation statements)

References 34 publications

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Section: Factors That Influence the Acoustic Performance Of Green Wallsmentioning

confidence: 67%

“…The absorption coefficient stays almost unchanged for lightweight soil at frequencies above 400 Hz and is observed to have a maximum decrease of around 0.2 at 160 Hz when increasing the moisture content. This effect has been further proved by the study done by Fabiani et al, 83 Horoshenkov et al, 43 and Attal et al 84 In terms of acoustic insulation, Fabiani et al 83 showed that the acoustic transmission loss is highly affected by the relative humidity content of the substrates. In the range of 10%-30%, increasing water contents generally leads to better sound insulation, while the effect is limited at higher levels, that is, 90%.…”

Section: Substratementioning

confidence: 83%

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A review of the application of green walls in the acoustic field

Yan

2022

Building Acoustics

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Green wall technology, including green façades and living walls, presents a promising solution to encounter the negative impacts of noise pollution. Research and development of green walls are steadily progressing in multiple fields, including but not limited to the environmental, social, and economic areas. Compared to other themes, the number of acoustic studies of green walls is relatively low and lacks relevant review papers. The purpose of this paper is to give a systematic review of the application of green walls in the acoustic field and clarify the key factors that influence the acoustic performance of green walls and the main obstacles that obstruct the broader application of green walls. A total number of 34 papers published in the past 10 years are reviewed. This study identifies that the acoustic applications of green walls are mainly in four aspects, namely laboratory applications, outdoor applications, indoor applications, and audio-visual applications. Vegetation morphology and properties of substrates are the two crucial factors determining green facades and living walls’ acoustic properties, respectively. High installation, operation, and maintenance costs and plant-induced problems are recognized as the main obstructions. A few possible topics are recommended for future study as well.

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Section: Factors That Influence the Acoustic Performance Of Green Wallsmentioning

confidence: 67%

Section: Substratementioning

confidence: 83%

A review of the application of green walls in the acoustic field

Yan

2022

Building Acoustics

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“…Apart from that, vegetation promotes restoration by providing a pleasant visual environment, which reduces the burden of environmental noise (previous research indicates that visible green from home can achieve an equivalent noise level reduction in relation to annoyance of up to 10 dBA), and by providing a source of positive natural sounds such as bird songs [16]. Furthermore, the sound absorbing properties of urban vegetation can reduce urban noise levels and promote quite sides [17][18][19][20][21][22][23][24][25][26][27][28][29]. Road traffic noise can be reduced by 50 % when minimal roadside vegetation is replaced by medium roadside vegetation [20].…”

Section: Introductionmentioning

confidence: 99%

Characterisation of the acoustic impedance of vegetated roofs with a multiple-geometry approach

2022

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“…Tabla 5. Resumen de estudios sobre compósitos utilizados como absorbentes acústicos [13,28,29,30,31,32,33,34,35,36,37,38,39,40,41].…”

Section: Compósitosunclassified

Estudio de compósitos de fibras naturales y arcilla para aplicaciones acústicas

Martínez¹

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During the last decade, actions and studies to counteract the effects of noise have increased through the use of insulating or absorbent materials, and civil regulations based on monitoring in urban areas, since exposure to high levels of sound pressure can cause psychological and physiological health problems such as anxiety, depression, stress, fatigue, cardiac, hearing or cognitive problems, as well as irreversible hearing loss. This work aims to develop and study natural compounds made of clay reinforced with coconut or nopal fibers to analyze their acoustic coefficients and determine their applications as insulation or conditioning material. The composites were obtained incorporating 25, 50 and 75% by weight of each fiber with bentonite clay. The physical and chemical characterization of the composites was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical microscopy, Fourier transforms infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). The properties of hardness and apparent density of the composites were obtained from samples aged three months. Using XRD, the compounds were identified in the bentonite: montmorillonite, quartz and feldspar. The FT-IR allowed the identification of the functional groups of the clay and for the fibers the presence of lignin and hemicellulose was determined. Micrographs show that coconut fiber is more porous than nopal; the size of the nopal fibers was between 71.8 and 219.7 nm (electron microscopy) and that of the coconut fibers was 0.1613 mm (optical microscopy). The apparent density of the composites follows the model of the mixture rule, while the hardness changes very little in the samples prepared with nopal fiber. Through ATG it was found that bentonite improves the thermal stability of the composites. The acoustic absorption, reflection, and transmission coefficients of the materials were determined using the impedance tube method, in the range of 50 to 10,000 Hz. The samples obtained after the synthesis process was weighed and characterized in the impedance tube; For the humidity tests, a drop was placed on the surface of the sample and the characterization process was repeated. These tests were carried out until 4 drops of water were added to each composite. The results showed an increase in the acoustic absorption properties when adding the fibers in the composites, where it was observed that the coconut fiber presented a higher sound absorption than the nopal fiber. The hardness and density of the material are directly related to a reduction in the absorption coefficient, although the tests carried out show that the nopal fibers in the composites do not increase their hardness and their acoustic properties, unlike coconut fibers. The results obtained from the acoustic characterization carried out in the surface humidity test showed that the absorption, reflection and absorption coefficients of the coconut change with increasing humidity in the samples. While, in the case of nopal, due to its composition and hydrophobic properties, there is no significant variation in its acoustic properties. Composites made from coconut fiber have better acoustic absorption and reduction properties, while those made from nopal fiber stand out in terms of sound reflection.

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Experimental investigation of the effect of moisture on the acoustic properties of lightweight substrates used in green envelopes

Cited by 10 publications

References 34 publications

A review of the application of green walls in the acoustic field

A review of the application of green walls in the acoustic field

Characterisation of the acoustic impedance of vegetated roofs with a multiple-geometry approach

Estudio de compósitos de fibras naturales y arcilla para aplicaciones acústicas

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