The Absorption Characteristics of Empty Water Bottles
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TECHNICAL NOTE
The Absorption Characteristics of Empty Water Bottles Ahmed Elkhateeb1,3 · Soha Eldakdoky2 Received: 30 January 2020 / Accepted: 13 April 2020 © Australian Acoustical Society 2020
Abstract This work examines experimentally the absorption characteristics of empty plastic water bottles. It focuses on the three common sizes of bottles widely available in the Saudi market (1500, 600 and 330 ml). Measurements were performed according to ISO 354 and ISO 9613-1 standards in the reverberation chamber. Three systematic groups of measurements were performed, each of which examined only one of the three categories. Each group included four tests with a predetermined density (number of bottles per square meter) and alignment. The impact of combining the three sizes of the bottles in one configuration was tested as well. Then, the impact of filling the best absorptive bottle with sand and the impact of the bottles’ position and alignment were investigated. Results demonstrated that water bottles are not a true Helmholtz resonator, as there is more than one resonance frequency for each category. Nevertheless, their fundamental frequencies can be predicted with a certain degree of accuracy, by applying the equation for true Helmholtz resonators. Results showed that the absorption is directly proportionate to the density and the bottle volume. Using either medium or small water bottles alone does not yield a remarkable absorption, unlike large or mixed bottles, which give the best results. Sand has almost no effect on the absorption of sound. Finally, results demonstrate that a remarkably higher level of absorption is achieved in the mid- and high-frequency ranges by placing the 1500-ml bottles onto the floor of the room at random. Although the values of the different measures of absorption are not too high, results of the combined volumes seem promising. Further investigation to improve this absorption is required. Keywords Empty water bottles · Helmholtz resonators · Absorption coefficient · Reverberation chamber
1 Introduction Due to the increasing concern with environmental issues and their implications, researchers in the field of acoustics around the world are paying close attention to the recycling and reproduction of specific acoustic materials that are inexpensive and eco-friendly. Such activities have a twofold impact; on the one hand, they help to get rid of tonnes of waste material, and on the other they can provide affordable materials that can be easily utilized to improve the quality of life. In
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Ahmed Elkhateeb [email protected] Soha Eldakdoky [email protected]
1
Department of Architecture, Faculty of Engineering, Ain Shams University, Cairo, Egypt
2
Department of Architecture, Faculty of Engineering, Helwan University, Helwan, Egypt
3
Department of Architecture, Faculty of Environmental Design, King Abdulaziz University, Jeddah, Saudi Arabia
this context, the works of Nizamuddin [1], D’Alessandro and Pispola [2], Seddeq et al. [3], Aly et al. [4], Bansod et al. [5] and Chen
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