From airplanes to apartments, most spaces are now designed with sound-absorbing materials that help decrease various sounds of everyday life. But most of the sound-absorbing materials that can cancel out human voices, traffic noise and music are made from plastic foams (泡沫) that aren't easily recycled or degraded. Now, researchers reporting in ACS Sustainable Chemistry & Engineering have created a biodegradable film (薄膜) obtained from seaweed, which effectively absorbs sounds in this range.
Controlling and optimizing the way sound moves throughout a room is the key to creating functional spaces. Foam sound-absorbing panels are a common solution, and they come in a variety of materials and thicknesses tailored to specific sound requirements. Most of these foams, however, are made from a type of plastic material and other chemical substances that are obtained from natural oil or petrol. To avoid petrochemicals, researchers have explored more renewable sources and biodegradable sound-absorbing alternatives. But many current options are made from plant fibers that don't effectively decrease noises in the most useful range of sound frequencies, or they are too thick or difficult to produce. So, Chindam's team wanted to develop a biodegradable material from a plant, which would be simple to produce and could absorb a range of sounds.
The team created films of agar (琼脂), a material that comes from seaweed, along with other additives developed from plants and varied the thickness of the films. After running the materials through a battery of tests, the researchers measured how well the films reduced sound across a range of frequencies. To do this, the team created a sound tube in which a speaker is placed at one end, and the test film is fitted over the other end. Microphones in the middle of the tube measured the amount of sound sent by the speaker and the amount of sound reflected off the film. These experiments showed that the films with many small holes made with the highest concentrations of agar had the greatest sound-absorbing qualities and performed similarly to traditional sound-absorbing foams. The researchers plan to explore ways to change the agar films to give them other desirable properties, such as flame resistance, and will explore other biologically obtained film materials.
