Whether they're in cars, buildings or airplanes, most of today's noise-blocking acoustic tiles are made of petrochemical-derived foam. A more eco-friendly alternative may be on the way, however, in the form of seaweed-derived membranes.
Although plant-based materials have been explored for this application before, many have not blocked sound over a wide enough range of frequencies, or they've been too bulky to fabricate on a commercial level.
Seeking a more functional, "doable" alternative, scientists from the Indian Institute of Technology looked to a seaweed-derived gelatinous material known as agar. Combined with glycerine as a plasticizer and nanocrystalline cellulose as a reinforcement material, agar was spread out into thin films, which were then freeze-dried to create porous membranes.
The sound-blocking characteristics of those membranes were subsequently tested by placing a loudspeaker at one end of a tube, one of the membranes over the other end, and two microphones in the middle – one mic measured how much sound was emitted by the speaker, while the other measured how much of that sound was reflected back into the tube by the membrane.
It was found that membranes with about 80 percent porosity performed best over a wide range of frequencies "from a bass hum to a shrill whine," offering performance similar to that of traditional acoustic foams. Unlike those foams, however, the agar membranes wouldn't require petrochemicals for their production, plus they would biodegrade once discarded.
The scientists are now looking into adding other qualities to the membranes, such as flame resistance, and are also exploring the use of other plant-based materials.
A paper on the research, which is being led by Asst. Prof. Chindam Chandraprakash, was recently published in the journal ACS Sustainable Chemistry & Engineering.
Source: American Chemical Society via EurekAlert