In Japan, there are many spaces with poor sound absorption, such as nursery rooms, which should be improved as soon as possible. It is possible to immediately enhance the sound environment by utilizing low-cost and readily available materials that can be obtained anywhere. Thus, we have focused on bubble wrap, which is commonly used to protect fragile items in ordinary households, as one of the materials. Layering horizontally many bubble wrap sheets creates a multi-mass coupled vibration system, where a thin film and an air cap are stacked repeatedly and continuously. Therefore, the layered bubble wrap can exhibit peaks and drops in absorption performance, displaying a high sound absorption peak in the low-frequency range. In this presentation, assuming that the structure consists of N masses and air springs, we have derived formulae that can be used to calculate the fundamental resonance frequency, enabling the proper design of the sound absorption coefficient. In addition, we have shown the measured and calculated results of the normal incidence absorption coefficient for the N-layered bubble wraps to verify the formulae.
Sugie et al. (Wed,) studied this question.