Abstract
Nowadays, emerging noise pollution by external factors causes harmful diseases in human beings. The development of a bio-based filler or panel will help to eliminate some unwanted noise in working places and living rooms. This work aimed to develop an ecowaste fiber (leftover after harvesting)-based sound absorber and analyze its capabilities for sound absorption. The ecowaste fibers are collected by the gleaning process, i.e., the process of collecting leftovers from fields. The sound absorption capabilities of three natural fibers extracted from Eleusine coracana (Finger millet) straw, Desmostachya bipinnata (Darbha), and Typha domingensis (Ripe bulrush) plants are investigated in this study, both individually and in hybrid combinations. The sound absorption property mainly depends on factors such as porosity, flow resistivity, thickness, density, and tortuosity. Fiber length and fiber type play a significant role when fibers are arranged individually or in hybrid combinations. The stacking effect on the sound absorption coefficient of hybridized fiber arrangement was experimentally analyzed. The sound absorption coefficient (α) was found to be lower in the range of 1000 Hz–2500 Hz for all the combinations. As a homogenous fiber arrangement, the darbha fiber exhibited the better NRC (noise reduction coefficient) of 0.86 for 50 mm thickness among three different fibers and as a hybrid composition, ripe bulrush and darbha fibers exhibited NRC of 0.90 which is more capable of absorbing sound in the critical frequency range of 500 to 2000 Hz. These types of natural fiber fillers are highly capable of better sound absorbing and used in the applications such as classrooms, sound recording rooms, and theatres.
Highlights
In the modern era, one such issue is noise, and it is considered undesirable
Darbha fibers were extracted from darbha plants (Desmostachya bipinnata) grown along the Cauvery riverbanks and the ripe bulrush fibers from Typha domingensis, a weed plant that grows along the banks of lakes in the Mysuru district
sound absorption coefficient (SAC) decreases in the frequency range 1000 Hz–2500 Hz; it resumes its upward trend in the frequency range 2500 Hz–3500 Hz
Summary
One such issue is noise, and it is considered undesirable. Continuous exposure to noise levels of 80 dB or higher for more than eight hours a day increases tension and alters breathing patterns [1]. E result reveals that SAC is greater than 0.5 above 600 Hz, while the SAC exceeds 0.87 above 1750 Hz. the investigation on the sound absorption of the kenaf fiber based composite sample showed a better SAC of 0.89 by varying thicknesses and densities [29]. E present study aims to investigate the sound absorption properties (SAC-α and NRC) of finger millet straw, darbha, and ripe bulrush fibers for different thicknesses. Their hybrid combinations are investigated to understand the effect of hybridization and increase of thickness on the sound absorbing properties
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