Algae keep the peace | Technology networks

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From airplanes to apartments, most spaces are now designed with sound-absorbing materials that help dampen the buzzes, echoes and murmurs of everyday life. But most acoustic materials that can cancel out human voices, traffic, and music are made from plastic foams that aren’t easily recycled or degraded. Now researchers reporting in ACS Sustainable Chemistry & Engineering have created a biodegradable film derived from algae that effectively absorbs sound in this range.

Controlling and optimizing how sound travels through a room is key to creating functional spaces. Foam acoustic panels are a common solution, and they are available in a variety of materials and thicknesses to suit specific sound requirements. However, most of these foams are made from polyurethane and other polymers derived from crude oil or shale gas. To avoid petrochemicals, researchers explored more renewable and biodegradable sound deadening alternatives. But many of today’s options are made from plant fibers that don’t effectively attenuate noise in the most useful sound frequency range, or they’re too thick or difficult to make. So, Chindam Chandraprakash and his colleagues wanted to develop a plant-derived, biodegradable material that would be simple to manufacture and could absorb a range of sounds.

The team created thin films of agar, a jelly-like material that comes from algae, along with other plant-derived additives and varied both the thickness and the porosity of the films. . After running the materials through a battery of tests, the researchers measured how well the films attenuated sound across a range of frequencies – from a bass buzz to a shrill whine. To do this, the team created a sound tube in which a speaker is placed on one end and the test film is mounted on the other end. Microphones in the middle of the tube measured the amount of sound emitted from the speaker and the amount of sound reflected from the film. These experiments showed that the porous films made with the highest concentrations of agar had the greatest sound absorption qualities and behaved similarly to traditional acoustic foams. The researchers plan to explore ways to modify agar films to give them other desirable properties, such as flame resistance, and will explore other biobased film materials.

Reference: Kumar S, Jahan K, Verma A, Agarwal M, Chandraprakash C. Agar-based composite films as effective biodegradable sound absorbers. ACS Sustainable Chem Ing. 2022;10(26):8242-8253. doi:10.1021/acssuschemeng.2c00168

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