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.

这项工作通过实验检查了空塑料水瓶的吸收特性。它着重介绍了沙特市场上广泛使用的三种常见尺寸的瓶子（1500、600和330毫升）。根据混响室内的ISO 354和ISO 9613-1标准进行测量。进行了三组系统的测量，每组仅检查了三个类别之一。每个组包括四个具有预定密度（每平方米的瓶子数）和对齐方式的测试。还测试了将三种尺寸的瓶子组合成一种配置的影响。然后，研究了用沙子填充最佳吸收性瓶子的影响以及瓶子位置和对准的影响。结果表明，水瓶不是真正的亥姆霍兹共振器，因为每个类别都有一个以上的共振频率。尽管如此，通过将公式用于真正的亥姆霍兹谐振器，可以以一定的精度预测其基本频率。结果表明吸收率与密度和瓶的体积成正比。单独使用中型或小型水瓶不会产生明显的吸收，这与大瓶或混合水瓶效果最佳有关。沙对吸收声音几乎没有影响。最后，结果表明，通过将1500毫升的瓶子随机放置在房间的地板上，在中高频范围内可获得明显更高的吸收水平。尽管不同吸收率的测量值不太高，但合并体积的结果似乎很有希望。