A new type of fabric can reduce noise in two ways: by directly canceling sound through the emission of opposing sound waves or by preventing sound transmission.
A team of experts at the Massachusetts Institute of Technology (MIT), along with several other research institutes, has developed a thin fabric nearly as fine as human hair that significantly reduces noise, according to Interesting Engineering on May 7. This material contains a special type of fiber that can vibrate when voltage is applied. The research team has harnessed this vibration to cancel sound in two different modes.
Experts researching the new fabric that blocks noise. (Photo: MIT News).
The first mode involves the fabric vibrating to emit sound waves that counteract unwanted noise, similar to noise-canceling headphones. Specifically, to directly cancel sound, the research team has created a fabric speaker. They use it to emit sound waves that are opposite to the unwanted sound waves reaching the fabric, thereby canceling out the noise. However, this mode is only effective in small spaces, such as inside a person’s ear, and not effective in larger areas like rooms or airplanes.
The second mode keeps the fabric stationary to cancel vibrations, which are a key factor in sound transmission. For example, if a neighbor living in an adjacent apartment plays soccer at midnight, the person sleeping will hear the noise because the sound from the next apartment causes the shared wall to vibrate, generating sound waves on this side.
To cancel that sound, the research team can cover the shared wall on the side of the person sleeping with the new fabric, controlling the vibrations in the special fibers to keep the fabric still. This indirect vibration cancellation prevents sound from passing through the fabric, helping to reduce noise in larger spaces like rooms or cars.
In their new research, the team of scientists examined common materials such as silk, canvas, and muslin to create practical noise-canceling fabric. Their experiments revealed that the mechanical properties and hole size of the fabric affect its sound-canceling effectiveness. Although silk and muslin have similar mechanical properties, silk has smaller holes, making it a better fabric speaker. However, the effectiveness of hole size also depends on the frequency of sound waves. If the frequency is low enough, even fabrics with relatively large holes can operate efficiently.
When testing the new fabric in direct cancellation mode, the research team found that it could reduce noise by up to 65 decibels (comparable to the sound of a lively conversation). In the indirect vibration cancellation mode, the fabric can reduce sound transmission by up to 75%.
In the future, the research team aims to explore ways to use the new fabric to block sounds of various frequencies. This may require complex signal processing and additional electronic devices. Additionally, they want to further investigate the fabric structure to enhance performance.
“In a world where noise seems to overwhelm silence, our goal is to create tranquility, a commodity more precious than gold. By harnessing the power of the fabric’s vibrations, we are opening new possibilities for establishing quiet spaces,” said Grace Yang, the lead author of the study and an expert at MIT.
