Assessment of the performance of unplastered pet bottle masonry walls in noise reduction.
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Environmental noise has long been recognized as a nuisance affecting the quality of life and well-being with certain levels of it known to cause severe health problems to those who are exposed to it. Several noise mitigation strategies exist: a barrier may be constructed between the noise source and the receiving end. This barrier may be classified according to the acoustic comfort it avails. From the inception of the ecofriendly PET bottle masonry in the construction of walls for dwellings, little is known about the acoustic performance of this material. This research focused on assessment of the performance of unplastered PET bottle masonry walls in noise reduction and it zeroed in on the effect of composite wall density, effective wall thickness and the sound frequency of sound on the performance. Five unplastered PET bottle masonry wall models were erected using ‘bottle’ bricks bonded in cement and sand mortar with the designations; BSW (for 2l sand-filled bottle wall), MSW (for 500ml sand-filled bottle wall), SSW (for 330ml sand-filled bottle wall), SPW (for 330ml polyethene-filled bottle wall) and SAW (for 330ml air-filled bottle wall). The walls were tested for composite wall density using the displacement method for volume and their effective wall thicknesses determined in accordance to BS EN 1996-1-1:2005 Part 18.104.22.168. Their respective airborne sound insulation performance was tested in accordance to BS EN ISO 16283-1:2014 and finally, they were acoustically classified in based on ISO/DIS 19488. From the study, it was found out that increasing the composite density of the wall by using denser material as infill in the bottles of the wall brought about an increase in the sound reduction properties of the wall. This however is not true for other infill materials like air that have different sound attenuation mechanisms yet they are less dense. In effect, SAW performed better than the SPW yet it is less dense. Increasing the wall thickness also brought about better performance in the walls however, this result was compounded by an increase in the wall density with increase in thickness. Also, the more massive walls (BSW and MSW) performed best in the high sound frequency range compares to the less massive ones, yet the converse was true in the low sound frequency range where the less massive walls like SSW performed best in sound insulation. In accordance to ISO/DIS 19488, BSW, MSW and SSW was of acoustic class E while SAW was of class F and SPW was of no performance defined (npd) in space type 2. All walls were npd in space types 1 and 3.