A sound insulation method has been developed that suppresses up to 94% of noise - we tell how it works
American engineers have proposed a method of sound insulation. It differs from the usual sound-absorbing panels. This is a plastic ring printed on a 3D printer.
Photo by John Baer / CC BY-SA
Classic noise absorbing panels block the path to acoustic waves and quench sound energy, part of which is converted to heat. Due to the design features and the materials used, such panels practically do not let air through.
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Experts at Boston University have proposed a "breathable" plastic ring that blocks up to 94% of the noise. He was called the "acoustic metamaterial ".
The principle of the metamaterial is based on Fano resonance . When two waves interfere, their energy is distributed asymmetrically. As a result, at one point in space, the sound pressure rises to maximum values, and at another, it drops to almost zero.
This distribution of acoustic waves by researchers from Boston University was achieved 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, come into Fano resonance and calm down.
The authors of the technology developed a prototype device, which was printed on a 3D printer and installed on a PVC pipe, at the other end of which a speaker was located. And although the end of the pipe with the ring remained more than half open, the sound passing through it became noticeably quieter - in action you can see it in this video :
One of the advantages of the technology is the variety of possible “silencer” forms. According to the authors of the study, they were able to model noise absorbing nozzles with square and hexagonal cross sections - material of this form is proposed to be used as 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 to create prototypes standard for 3D printers, ABS plastic and epoxy resin .
But the invention has an obvious disadvantage - the need for individual calculation. Each device is designed for specific frequencies and sizes, so massively create universal rings will not work.
The direction of acoustic metamaterials has been evolving for several years. And work in this area, not only researchers from Boston. As an analogue, you can bring the device engineers from France - in 2016 they created a panel with a thickness of 1 cm, blocking low frequencies. Usually for suppressing low frequencies, panels up to 10 cm thick are required .
The French invention consists of rows of small Helmholtz resonator chambers that muffle the passing sounds. According to the authors of the solution, it can be used for sound insulation in buildings and transport - the panels take up little space and weigh a little, but at the same time block almost 100% of the sounds.
Another acoustic metamaterial was developed at the University of Southern California. It is a lattice structure 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 by Shunichi kouroki / CC BY
It is believed that developments in the field of acoustic metamaterials will expand the possible scope of sound insulation. Researchers expect that noise reduction innovations will help make the urban ecosystem more comfortable: metamaterials can be used to build soundproof screens along major highways.
Additional reading - we 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
New way to "absorb" sound
Classic noise absorbing panels block the path to acoustic waves and quench sound energy, part of which is converted to heat. Due to the design features and the materials used, such panels practically do not let air through.
')
Experts at Boston University have proposed a "breathable" plastic ring that blocks up to 94% of the noise. He was called the "acoustic metamaterial ".
The principle of the metamaterial is based on Fano resonance . When two waves interfere, their energy is distributed asymmetrically. As a result, at one point in space, the sound pressure rises to maximum values, and at another, it drops to almost zero.
This distribution of acoustic waves by researchers from Boston University was achieved 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, come into Fano resonance and calm down.
The authors of the technology developed a prototype device, which was printed on a 3D printer and installed on a PVC pipe, at the other end of which a speaker was located. And although the end of the pipe with the ring remained more than half open, the sound passing through it became noticeably quieter - in action you can see it in this video :
Advantages and disadvantages
One of the advantages of the technology is the variety of possible “silencer” forms. According to the authors of the study, they were able to model noise absorbing nozzles with square and hexagonal cross sections - material of this form is proposed to be used as 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 to create prototypes standard for 3D printers, ABS plastic and epoxy resin .
But the invention has an obvious disadvantage - the need for individual calculation. Each device is designed for specific frequencies and sizes, so massively create universal rings will not work.
Analogs of the Invention
The direction of acoustic metamaterials has been evolving for several years. And work in this area, not only researchers from Boston. As an analogue, you can bring the device engineers from France - in 2016 they created a panel with a thickness of 1 cm, blocking low frequencies. Usually for suppressing low frequencies, panels up to 10 cm thick are required .
The French invention consists of rows of small Helmholtz resonator chambers that muffle the passing sounds. According to the authors of the solution, it can be used for sound insulation in buildings and transport - the panels take up little space and weigh a little, but at the same time block almost 100% of the sounds.
Another acoustic metamaterial was developed at the University of Southern California. It is a lattice structure 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 by Shunichi kouroki / CC BY
findings
It is believed that developments in the field of acoustic metamaterials will expand the possible scope of sound insulation. Researchers expect that noise reduction innovations will help make the urban ecosystem more comfortable: metamaterials can be used to build soundproof screens along major highways.
Additional reading - we prepared a mini-digest with materials from our “ Hi-Fi World ”, which are devoted to silence and the fight against noise pollution:
- What is useful (and dangerous) around us "noise" . We talk about the harm that causes our health to the noise of cities and streets and what can be done about it. We will also talk about the “other side of the coin” - the beneficial properties of sounds and music therapy.
- There is a lot of noise, there will be little noise: sound hygiene in cities . We discuss the sound landscape of modern cities. We give tips on soundproofing housing and offices and recommendations on the choice of anti-noise gadgets.
- Stronger to sleep and work better - as music helps to deal with noise . We talk about how the music protects from extraneous noise during sleep and during work. We also collected recommendations on how to listen to music during work hours without harming productivity and hearing. The article will be useful to those who work in the open-space or coworking.
- “Start the week right”: which gadgets will help reduce ambient noise and “catch” concentration . A detailed analysis of different types of devices for noise reduction - from "classic" headphones and earplugs to massive helmets, similar to gadgets from sci-fi movies.
- Headphones with active noise cancellation: do not hear anyone, hear nothing . We are talking about the features of earbuds and ear cushions for headphones with enhanced sound insulation, as well as the intricacies of picking gadgets with active noise cancellation.
- “Do not 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 that of hearing. We talk about the sources of noise in restaurants and cafes and how the owners and visitors of institutions can deal with excessively loud sounds in the room.
- How to make a soundproof ceiling with their own hands . This is an article guide, and it describes all the steps: from project development to redecoration. Also here is a list of necessary materials and the calculation of their value.
Source: https://habr.com/ru/post/444094/
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