New Material: MIT Researchers Have Developed A Silk Fabric That Uses Vibration To Suppress Sound

MIT researchers have developed a kind of silk fabric, whose thickness is only a little thicker than human hair, which can suppress unnecessary noise and reduce the spread of noise in large rooms. Photo source: MIT News; iStock

We live in a world of constant noise. From the buzz of heavy traffic outside, to the noisy TV set in the neighborhood, to the chatter in the cubicle of colleagues, endless noise has always been a challenge we face.

To solve this problem, interdisciplinary research teams at MIT and other institutions have developed an innovative silk fabric designed to suppress sound and create a quieter space.

This kind of fabric is as thin as hair, and has a special fiber that will vibrate when voltage is applied. The researchers used these vibrations to suppress sound in two different ways.

The first method is to use the fabric to generate sound waves to interfere with and eliminate unnecessary noise, just like noise reduction earphones. However, although this technology is effective in a small area, it is not practical in large spaces such as rooms or aircraft.

The second and more surprising technique is to keep the fabric still, thus blocking the vibration of sound transmission. By preventing the transmission of sound, this fabric can significantly reduce the noise in large areas, so it is very suitable for use in rooms or vehicles and other spaces.

Fabric can suppress sound by generating sound waves, which will interfere with unwanted noise and eliminate it (as shown in Figure C), or suppress vibration by staying still, which is the key to sound transmission (as shown in Figure D As shown in). Image source: provided by researchers

By using common materials such as silk, canvas and tulle, researchers have created noise suppression fabrics that can be applied in real space. For example, people can use this fabric to make partitions in open working spaces or thin fabric walls to prevent sound penetration.

"Noise is easier to make than quiet. In fact, in order to isolate noise, we use a lot of space to build thick walls. "Yoel, professor of the Department of Materials Science and Engineering, Department of Electronic Engineering and Computer Science, chief researcher of the Electronic Research Laboratory, and senior author of papers on fabrics Fink) said, "[The first author] Grace's research provides a new mechanism for creating quiet space with thin fabrics."

The first author of this study is Grace (Noel) Yang, a doctor of 21 SM and 24. Co authors include MIT graduate student Taigyu Joo, Hyunhee Lee, Henry Cheung and Yongyi Zhao; Zachary, Robert Noyes Professor of Chemical Engineering Career Development, Massachusetts Institute of Technology Smith; Guanchun Rui, a graduate student and Lei Zhu, a professor of Case Western Reserve University; Jinuan Lin, a graduate student and Chu, an assistant professor at the University of Wisconsin Madison Ma; and Latika Balachander, a graduate student at Rhode Island School of Design. An open access paper on this research was published in Advanced Materials.

This sound suppression silk was developed on the basis of the fabric microphone made by the team before.

In this study, they sewed a single strand of piezoelectric fiber into the fabric. Piezoelectric materials generate electrical signals when they are squeezed or bent. When the nearby noise causes the fabric vibration, the piezoelectric fiber will convert these vibrations into electrical signals to capture the sound.

In this new study, researchers overturned this idea and created a fabric speaker that can be used to counteract sound waves.

"Although we can use fabrics to make sound, there is already too much noise in our world. We believe that it may be more valuable to create silence," Yang said.

Applying an electrical signal to a piezoelectric fiber causes it to vibrate, producing sound. The researchers demonstrated this by playing Bach's "Air" with 130 micron long silk flakes mounted on a circular frame.

In order to achieve direct sound suppression, researchers use silk fabric speakers to emit sound waves, which can destructively interfere with unwanted sound waves. They control the vibration of piezoelectric fiber, so that the sound wave emitted by the fabric is opposite to the unwanted sound wave hitting the fabric, thus canceling the noise. However, this technology can only be effective on a small scale. Therefore, based on this idea, researchers have developed a technology that uses fabric vibration to suppress the sound in a larger range (such as the bedroom).

Suppose your next door neighbor plays table football in the middle of the night. You will hear noise in the bedroom, because the sound in their apartment will cause the vibration of your shared wall, thus forming sound waves on your side. In order to suppress this sound, researchers can place the silk fabric on your side of the shared wall to control the vibration of the fiber and force the fabric to stay still. This vibration mediated suppression can prevent sound transmission through the fabric.

Yang said, "If we can control these vibrations and stop them from happening, we can stop the noise."

Surprisingly, researchers found that keeping the fabric still would make the sound reflected by the fabric, so that a thin piece of silk could reflect the sound like a mirror reflecting light. Their experiments also found that the mechanical properties and pore size of the fabric will affect the sound production efficiency. Although silk and tulle have similar mechanical properties, silk has smaller pores, making it a better fabric speaker. However, the effective pore size also depends on the frequency of acoustic waves. Yang said that if the frequency is low enough, even fabrics with relatively large pores can work effectively.

When testing the direct suppression mode of silk fabrics, the researchers found that it can significantly reduce the volume of sound, up to 65 decibels (similar to the voice of human passionate conversation). In the suppression mode with vibration as the medium, silk fabric can reduce the sound transmission by 75%.

Fink said that the achievement of these achievements should be attributed to a group of strong collaborators. Postgraduates from Rhode Island School of Design helped researchers understand the structural details of fabrics; Scientists at the University of Wisconsin Madison conducted the simulation; Researchers from Case Western Reserve University characterized the materials; The chemical engineers of the Smith Group at MIT used their expertise in gas membrane separation to measure the airflow through the fabric.

Looking ahead, researchers hope to explore how to use their fabrics to block the sound of multiple frequencies. This may require complex signal processing and additional electronic equipment. In addition, they also want to further study the fabric structure to understand how changing the number of piezoelectric fibers, stitching direction or applied voltage can improve performance.

"We can turn many knobs to make this silencing fabric really effective. We want people to think about how to control structural vibration to suppress sound. This is just the beginning," Yang said.