Undesirable sounds accompany residents of large cities round the clock, from traffic noise outside to the murmuring of a television behind the wall. This constant exposure to noise leads to increased fatigue, nervousness, and illness among us. To reduce noise pollution, specialists from the USA have developed sound-absorbing fabric no thicker than a human hair, which could become an ideal material for soundproofing residential spaces.
Previously, a team of scientists from the Massachusetts Institute of Technology worked on creating a microphone from piezoelectric threads, which generate electricity in response to mechanical deformation, in this case, due to sound waves. They then decided to develop a device with the opposite effect, as reported by EurekAlert.
“While we could use fabric to create sound, there’s already enough sound in the world,” said Grace Young, head of the research group. “We thought creating silence would be much more useful.”
Under the influence of an electrical signal, the piezoelectric fibers begin to vibrate, generating sound. To dampen unwanted noise, scientists created a speaker from silk fabric that suppresses undesirable noise. By controlling the vibrations of the piezoelectric fibers so that the sound waves of the fabric are opposite to the unwanted waves, they were able to neutralize them. This is the first mode, similar to the action of noise-canceling headphones. It works well in a small space, such as an ear canal, but is not suitable for large rooms.
However, as scientists found out, there is a second, more intriguing mode. If the fabric threads are stationary, they suppress the transmission of sound waves, reflecting them like a mirror does light rays. So, if you cover a wall with this material, the sounds that disturb your sleep simply won’t penetrate the room. “If we can control these vibrations and stop them at their source, we can also suppress the noise that creates them,” said Young.
Noise suppression tests showed that in the first mode, silk fabric can effectively suppress sound levels up to 65 dB, while in the second mode, the transmission of sound waves is reduced by 75%.
In the future, scientists plan to test the possibility of suppressing sound waves of various frequencies. This will likely require more complex signal control and the use of additional electronics. Additionally, they intend to further explore the structure of the fabric.
Several years ago, scientists discovered that certain types of moths protect themselves from bats by growing sound-absorbing scales on their bodies. It turned out that this structure could be replicated in artificial materials, resulting in a soundproofing material as thick as a dense sheet of paper.
