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Research group investigates acoustics and eliminates noise

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Associate Professor Hans Rämmal says, “Acoustics is related to audible and inaudible (outside human hearing range) sounds in the surrounding environment. Acoustic engineers are engaged in designing an acceptable environment for humans by insulating and damping unpleasant sounds, i.e. noise. High sensitivity of the human ear causes us also problems, because we hear noise as well (traffic noise through doors, windows, buildings, etc.). Noise as such can also be referred to as acoustic disturbance.”

The technical acoustics and vibrations research group is focused on designing acoustic materials for insulating and damping noise.  The objective is to develop lightweight, compact, reliable, low cost, noise control elements with high damping performance.
“A major issue with the use of conventional noise insulation materials is their overall dimensions (in particular thickness of the material) required for achieving higher damping performance, especially when aiming low frequency performance”, Hans Rämmal, one of the few acoustic engineers in Estonia with a PhD, explains.

The research group, in cooperation with the scientists of the Faculty of Chemical and Materials Technology, are studying and developing a perspective material –  aerogel that could be used in noise control applications. It is a novel material with supremely low density, which is achieving increasing global recognition. With low density and high porosity, this material can substitute a wide range of conventional porous materials used for noise cancellation purposes.
Micro-perforated panels constitute another promising future material in acoustical engineering.
“Both objects of research – the gel as well as the panels – will most likely be used in transportation noise control panels, driver’s cabs, engine flow ducts and construction of buildings,” Hans Rämmal explains.

“We also provide acoustics expert advice,” Rämmal adds. “In Estonia expert advice is often sought only in a conflict situation, when it is necessary to reduce noise of a finished product or building. An example that can be pointed out is a new development area, where the adjacent highway caused excessive traffic noise. Another example is a newly built power plant, the operator room of which turned out to be so noisy that working there posed a health risk.  “In such cases the experts of our research group identify the actual causes of the noise and provide methods for noise cancellation. In other countries an acoustics expert is involved already in the initial stage of construction or production,” he explains.
A good example in this context is cooperation with the large-scale enterprise ABB in the form of training and with an Estonian manufacturer of exclusive motorcycles Renard Motorcycles for whom a muffler with micro-perforated panels was developed.

In the near future a room acoustics testing centre will be completed containing special equipment for measuring sound transmission through building structures (incl. glass panels, doors, stone walls). “When the testing center is launched, we can start developing new state-of-the-art structural elements (e.g. windows, doors, partitions) that have improved acoustic performance. Our nearest competitors in this field are located in Espoo and Riga; we are the only ones in Estonia at present,” Associate Professor Hans Rämmal adds.

As environmental awareness in increasing, acoustics is becoming an increasingly important topic in the world. For example, in engine industry noise and exhaust emissions are the two most strictly limited indicators.

However, the other side of the coin is the so-called noise-freaks community. It is a known fact that approximately 80 per cent of the motorcycle mufflers complying with the required noise level produced by one of the most well-known major manufacturers are, at the earliest opportunity, replaced by muffles that make a stronger and “more original” noise even before they leave the store. Noise as a sound is becoming more and more a  brand-identifying feature, a part of a trademark and product,” Hans Rämmal explains.

Additional information: Hans Rämmal, Associate Professor at the Chair of Automotive Engineering of Tallinn University of Technology, hans.rammal@ttu.ee

Original post by Tallinn University of Technology

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