A sound insulation method has been developed that dampens up to 94% of noise - tell how it works
American engineers have proposed a method of noise isolation. It differs from the usual sound-absorbing panels. This is a 3D-printed plastic ring.
Photo by John Baer / CC BY-SA
Classic sound absorbing panels block the path of acoustic waves and dampen sound energy, some of which is converted into heat. Due to the design and materials used, such panels practically do not allow air to pass through.
Specialists at Boston University have proposed a “breathing” plastic ring that blocks up to 94% of noise. He was called "acoustic metamaterial ."
The principle of operation of the metamaterial is based on the Fano resonance . When two waves interfere, their energy is distributed asymmetrically. As a result, at one point in space, sound pressure rises to maximum values, and at another point it decreases to almost zero.
Researchers from Boston University managed to achieve this distribution of acoustic waves using a special form of metamaterial - inside the ring there is a spiral channel through which sound passes. Acoustic waves in this channel are reflected from the walls, enter the Fano resonance, and fall silent.
The authors of the technology developed a prototype of the device, which was printed on a 3D printer and installed on a polyvinyl chloride pipe, at the other end of which a speaker was placed. And although the end of the pipe with the ring remained open for more than half, the sound passing through it became noticeably quieter - in action you can see in this video :
One of the advantages of the technology is the variety of possible forms of a “silencer”. According to the authors of the study, they were able to simulate noise absorbing nozzles with a square and hexagonal section - they propose using this material in the form of building blocks for soundproof partitions.
The second advantage is low cost. The device can be made of any plastic, and it does not require special expensive materials. For example, the authors of the technology used ABS plastic standard and epoxy to create prototypes for 3D printers .
But the invention has an obvious drawback - the need for individual calculation. Each device is designed for specific frequencies and sizes, so it’s impossible to create universal rings in large quantities.
The direction of acoustic metamaterials has been developing for several years. And not only researchers from Boston are working in this area. As an analogue, one can bring the device of engineers from France - in 2016 they created a panel 1 cm thick that blocks low frequencies. Typically, up to 10 cm thick panels are required to suppress low frequencies . The
French invention consists of rows of small Helmholtz resonator chambers that drown out transmitted sounds. According to the authors of the solution, it can be used for noise insulation in buildings and vehicles - panels take up little space and weigh a little, but block almost 100% of sounds.
Another acoustic metamaterialdeveloped at the University of Southern California. It is a lattice structure made of plastic with iron particles, created using a 3D printer. Under the influence of a magnetic field, these particles move, which changes the structure of the material and its acoustic characteristics.
Photo Shunichi kouroki / CC BY
It is believed that developments in the field of acoustic metamaterials will expand the possible field of application of sound insulation. Researchers expect innovation in the area of noise absorption to help make the urban ecosystem more comfortable: metamaterials can be used to build noise screens along major highways.
Additional reading - we have prepared a mini-digest with materials from our “ Hi-Fi World ”, which are devoted to silence and the fight against noise pollution:
Photo by John Baer / CC BY-SA
A new way to “absorb” sound
Classic sound absorbing panels block the path of acoustic waves and dampen sound energy, some of which is converted into heat. Due to the design and materials used, such panels practically do not allow air to pass through.
Specialists at Boston University have proposed a “breathing” plastic ring that blocks up to 94% of noise. He was called "acoustic metamaterial ."
The principle of operation of the metamaterial is based on the Fano resonance . When two waves interfere, their energy is distributed asymmetrically. As a result, at one point in space, sound pressure rises to maximum values, and at another point it decreases to almost zero.
Researchers from Boston University managed to achieve this distribution of acoustic waves using a special form of metamaterial - inside the ring there is a spiral channel through which sound passes. Acoustic waves in this channel are reflected from the walls, enter the Fano resonance, and fall silent.
The authors of the technology developed a prototype of the device, which was printed on a 3D printer and installed on a polyvinyl chloride pipe, at the other end of which a speaker was placed. And although the end of the pipe with the ring remained open for more than half, the sound passing through it became noticeably quieter - in action you can see in this video :
Advantages and disadvantages
One of the advantages of the technology is the variety of possible forms of a “silencer”. According to the authors of the study, they were able to simulate noise absorbing nozzles with a square and hexagonal section - they propose using this material in the form of building blocks for soundproof partitions.
The second advantage is low cost. The device can be made of any plastic, and it does not require special expensive materials. For example, the authors of the technology used ABS plastic standard and epoxy to create prototypes for 3D printers .
But the invention has an obvious drawback - the need for individual calculation. Each device is designed for specific frequencies and sizes, so it’s impossible to create universal rings in large quantities.
Analogs of the invention
The direction of acoustic metamaterials has been developing for several years. And not only researchers from Boston are working in this area. As an analogue, one can bring the device of engineers from France - in 2016 they created a panel 1 cm thick that blocks low frequencies. Typically, up to 10 cm thick panels are required to suppress low frequencies . The
French invention consists of rows of small Helmholtz resonator chambers that drown out transmitted sounds. According to the authors of the solution, it can be used for noise insulation in buildings and vehicles - panels take up little space and weigh a little, but block almost 100% of sounds.
Another acoustic metamaterialdeveloped at the University of Southern California. It is a lattice structure made of plastic with iron particles, created using a 3D printer. Under the influence of a magnetic field, these particles move, which changes the structure of the material and its acoustic characteristics.
Photo Shunichi kouroki / CC BY
findings
It is believed that developments in the field of acoustic metamaterials will expand the possible field of application of sound insulation. Researchers expect innovation in the area of noise absorption to help make the urban ecosystem more comfortable: metamaterials can be used to build noise screens along major highways.
Additional reading - we have prepared a mini-digest with materials from our “ Hi-Fi World ”, which are devoted to silence and the fight against noise pollution:
- How useful (and dangerous) is the "noise" surrounding us . We talk about the harm that the noise of cities and streets causes to our health, and what can be done about it. We also talk about the “other side of the coin” - the beneficial properties of sounds and music therapy.
- There was a lot of noise, there would be little noise: sound hygiene in cities . We discuss the sound landscape of modern cities. We give advice on sound insulation of housing and offices and recommendations on the selection of anti-noise gadgets.
- Better sleep and better work - how music helps fight noise . We talk about how music protects against extraneous noise during sleep and during work. And we also collected recommendations on how to listen to music during working hours without harming productivity and hearing. The article will be useful to those who work in open space or coworking.
- “Start the week right”: which gadgets will help reduce ambient noise and “catch” the concentration . A detailed analysis of different types of devices for noise reduction - from the "classic" headphones and earplugs to massive helmets, similar to gadgets from science fiction films.
- Active noise canceling headphones: do not hear anyone, do not hear anything . We are talking about the features of the nozzles and ear pads for headphones with enhanced sound insulation, as well as the intricacies of the selection of gadgets with active noise reduction.
- “Don't make me loud”: why cafes and restaurants have become so noisy, and what to do about it . In public places, the average noise level is one third higher than safe for hearing. We talk about the sources of noise in restaurants and cafes and how owners and visitors to establishments can deal with excessively loud noises in the room.
- How to make a soundproof ceiling with your own hands . This is a guide article, and it describes all the stages: from project development to cosmetic repairs. Also here is a list of necessary materials and a calculation of their cost.