Sound absorption measurements of air-filled latex balloons

This paper reports on the sound absorption measurements of air-filled balloons. Balloons can be used for simple and economical acoustic treatment in rooms where, for aesthetic or functional reasons, it is not possible to permanently install sound-absorbing materials, or where rapid acoustic correction is required. In this study, balloons were those typically used for children’s parties, with an average diameter of 10 cm. Acoustic measurements were initially carried out in an empty room with plaster walls and a sufficiently long reverberation time. The room was then filled with balloons to cover the floor surface. The sound absorption coefficient was determined from the difference in reverberation times measured in the empty room and in the room containing balloons. Significant absorption at low frequencies was observed. Additional measurements of the balloons’ absorption coefficient were performed using an impedance tube (Kundt tube), and the effects of arranging balloons in series and of using double balloons—one inserted into the other—were evaluated. The latter configuration was found to yield the maximum acoustic absorption coefficient.