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Research Professor Johan Christensen, along with colleagues plastic foam Asger Mortensen plastic foam and Morten Willatzen from DTU Photonics developed a new method plastic foam for making sound absorbing structures which suppress noise in a wide frequency range. plastic foam
Inspiration comes from the optic where it is possible to achieve very high absorption by coating a material having plastic foam upstanding carbon nanotubes. Here we exploit plastic foam the carbon nanotube absorbs the light and that the spaces between the tubes are effective to capture the light, and in this way in the United States plastic foam researchers have created the world's darkest material.
The relationship between the frequency of visible light and sound in the kilohertz range is approximately 10 ^ 11th This also means that the relationship between the dimensions of the elements of the optical cladding and the acoustic cladding is many orders of magnitude plastic foam different. Where carbon nanotube plastic foam dimensions are measured in nanometers, the corresponding elements in the acoustic structure therefore be measured in centimeters.
They are placed as a grid with varying 'filling plastic foam factor', where 100 per cent. indicates that the fins are in contact with each other, and 50 per cent. indicates that the gap between the vanes is the same as the width of the slats.
Both theoretically and experimentally, the Danish-Spanish research has shown that the lower the filling factor is -, and thus the smaller plastic foam the noise-absorbing material is used - the better the noise absorption gets in the examined frequency plastic foam range from 0.7 to 3.0 kHz, which is selected because it is relevant in connection with traffic noise.
A reduction of the filling factor of 70 per cent. to 40 per cent. increases the average absorption of 97 per cent. to 99 per cent., explained plastic foam the researchers in their article, published in Nature journal Scientific Reports.
In fact, the calculations show that it will be an advantage to go down to a filling factor of 30 per cent. or even lower. However, since in practice it is difficult to produce the lamella structure with a filling factor below 40 per cent., It is this value, he believes it would be best to use in practice.
It amazes immediately plastic foam that he decides to find the attenuation by measuring the emitted and reflected instead of measuring plastic foam the transmitted directly to the appropriate side of the wall. There seems to conclude an additional equation, and some additional assumptions about the microphone exact location of the chosen method. Any comments / explanation?
The curve for the test with 30% fitting factor shows a worse result than 40-70% fitting factor. Why have you chosen to include this curve if other circumstances that can not be compared plastic foam with the other. Or at least include a note about why it differs.
It is then a well-known noise cancellation principle to use structures that stick out from the wall, however, it is normal to use the triangular structures on the one hand does not leave blank wall, and secondly do not have parallel faces opposite each other which are created for a single resonance frequency.
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