Noise inside endangered cars

2002/01/25 Andonegi Beristain, Garazi - Elhuyar Zientziaren Komunikazioa

• Elektronika

This system will reduce 6 decibels the internal noise of cars that normally is 60 decibels. Although this decrease seems small, it is the highest achieved so far. The difference between 60 and 50 decibels is comparable to the noise we hear in the car with the windows open and the noise we hear at 30 meters.

The system works on the effect of the counterposed phase waves, that is, when a sound wave joins another identical sound wave, counterposed in phase, both disappear. To achieve this effect, several transducers attached to the speakers are placed in the car. This technique, called active control, is used to reduce the noise of aircraft, boats and machines.

Sound of vibration

When the car travels on the road, it is much more difficult to eliminate the sound produced by the vibrations of the wheels and other parts. To measure this noise that is received through the suspension, the sensors should be distributed throughout the car, since there is not the only appropriate area to receive this vibration.

This has led them to direct their research into a simpler system. The sensors have been placed only on the front suspension of the car. This has significantly reduced noise in the driver's head and side areas.

If you want to reduce noise in the rest of the car, you should increase the number of transducers and speakers. This would greatly increase the complexity of the signals received and greatly hinder the coordination of all of them.