Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Noise quietens driving

28.01.2002


Sensors and loudspeakers reduce in-car racket.


Road block: anti-sound could stop drivers getting hoarse.
© Photodisc



Tired of shouting to your passenger as you drive, striving to make your voice heard over the rumble of the car? Help is on the way, in the form of strategically placed sensors and loudspeakers.

Researchers at the Korea Advanced Institute of Science and Technology (KAIST) in Taejon have developed a prototype system that shaves up to 6 decibels off the typical motoring noise of around 60 decibels. That’s more than any other comparable method1.


The difference between 60 and 50 decibels is like that between the noise inside a car with the windows down, and the same noise heard from about 30 metres away. Forty decibels is about the same level as a humming refrigerator. The KAIST system isn’t quite there yet, but it’s a good start.

The system uses anti-sound. Sound travels as pressure waves in air. Two sets of identical waves that are perfectly out of phase cancel one another out, just as two people jumping out of sync on a trampoline eliminate each other’s bounce.

Vibration sensors - transducers, rather like microphones - are hooked up to loudspeakers. When the sensors detect noise, a signal tailored to counteract it is almost instantaneously constructed. This technique, called active control, reduces background noise in aircraft, machinery and ships.

Sonic boom

Road booming noise - the din inside a car created by vibrations in the wheels that are transmitted through the suspension - is particularly difficult to eliminate. It depends on speed, road surface and suspension, among other factors. It is thus more variable than the steady drone of aircraft or machinery.

As a result, there is no single ideal location for vibration transducers in all vehicles. And the computational demands of converting the transducer signal into an anti-sound output at the loudspeakers means that active-control systems struggle to respond fast enough to changing noise levels.

Nevertheless, Shi-Hwan Oh and colleagues at KAIST have come up with a relatively simple system that gives a fair reduction in noise.

In principle, the best way to measure motoring noise vibration would be to cover the vehicle with transducers. But if there are too many, it is impossible to combine all their inputs into an anti-sound response. A good compromise, the researchers find, is four transducers attached to the left and right front suspension system.

Similar tests helped them to locate the best positions for the loudspeakers: on the floor behind the two front seats. This creates sweet spots of noise reduction around the heads of the driver and front passenger.

Oh’s team also designed an algorithm that converts the transducer signals quickly and efficiently into a loudspeaker output signal. To reduce noise elsewhere in the car, more transducers and speakers would be needed, which would increase the complexity of the computations.


References

  1. Oh, S.-H., Kim, H.-S. & Park, Y. Active control of road booming noise in automotive interiors. Journal of the Acoustical Society of America, 111, 180 - 188, (2002).


PHILIP BALL | © Nature News Service
Further information:
http://www.nature.com/nsu/020121/020121-12.html

More articles from Transportation and Logistics:

nachricht New players, standardization and digitalization for more rail freight transport
16.07.2018 | Fraunhofer-Institut für System- und Innovationsforschung (ISI)

nachricht A helping (Sens)Hand
11.04.2018 | Fraunhofer-Institut für Arbeitswirtschaft und Organisation IAO

All articles from Transportation and Logistics >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Nonstop Tranport of Cargo in Nanomachines

Max Planck researchers revel the nano-structure of molecular trains and the reason for smooth transport in cellular antennas.

Moving around, sensing the extracellular environment, and signaling to other cells are important for a cell to function properly. Responsible for those tasks...

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Optical Coherence Tomography: German-Japanese Research Alliance hosted Medical Imaging Conference

19.11.2018 | Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

 
Latest News

Nonstop Tranport of Cargo in Nanomachines

20.11.2018 | Life Sciences

Researchers find social cultures in chimpanzees

20.11.2018 | Life Sciences

When AI and optoelectronics meet: Researchers take control of light properties

20.11.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>