PARK RIDGE, Ill. Engineers from Siemens Automotive have developed an electronic module that will control the noise from a car's air induction system, the company said.
The electronic Active Noise Control system attaches to an air-intake manifold a low-cost chunk of under-hood plastic and turns it into a smart device capable of listening to and canceling out unwanted noises on a vehicle. In doing so, it could solve a longstanding problem for automakers, while saving them money and freeing up under-hood space at the same time. "We hope to change the way automotive engineers think about noise control," said Dave Geran, director of business development for Siemens Automotive Air-Fuel Module Division (Windsor, Ontario).
Siemens reportedly is working with an unnamed automaker to develop the technology for production vehicles.
The new system is believed to be the first electronic means of solving the problem of air induction noise, which has been a problem since auto makers changed to plastic intake manifolds during the late 1980s.
The Active Noise Control system consists of a microphone, an electronics module, and a speaker mounted at a vehicle's air induction system. While the car's engine is running, the system monitors noise through the microphone. Analog signals from the microphone pass through an A/D converter, and go to a digital signal processor (DSP), which determines their frequency. The DSP then produces an opposing output signal and sends it to the speaker. The frequency of the output signal then cancels the noise of the air intake.
Siemens engineers said that such noise cancellation techniques have long been used by the military to drown out sounds in aircraft cockpits. The techniques have also been employed experimentally in the past by automakers as means of eliminating noise in passenger compartments. Up to now, however, no automaker has used those methods to deal with noise at the engine. "We are attacking real noise at its source," Geran said. "This system not only cancels out the noise that the driver hears, it cancels noise that the man on the street hears."
If auto manufacturers adopt the new technology, Siemens engineers said it could help them reduce noise without raising costs or causing under-hood packaging problems. In that respect, Active Noise Control could offer an advance over mechanical resonators, which are commonly used today, particularly in luxury cars. Plastic resonators, which also cancel engine noise by creating opposing frequencies, can be as large as a football and often cost as much as $10 each. Some luxury vehicles are said to use as many as 12 resonators. And engineers, who are often pressed to find extra space in a vehicle, typically struggle to find space for resonators.
Air induction noise has been a growing problem for automotive engineers since they changed over to plastic intake manifolds during the late 1980s. Because plastic manifolds vibrate more than the old aluminum manifolds, they creates noise problems. But auto makers don't want to change back to aluminum because plastic offers cost and weight advantages.
The new technology would enable automakers to keep using plastic manifolds while eliminating the need for resonators. "This is like having an infinite number of resonators," Geran said. "It allows you to deal with multiple frequencies across your engine's torque curve, all the way from zero rpm to 5,000 rpm."
Siemens executives said the technology could even enable automotive engineers to tune a vehicle's noise signature, thus making a luxury car sound smoother or a sports car sound throatier. "We first want to make the vehicle quieter," Geran said. "But we also want to support development of distinct sound signatures to help automakers with their brand strategies."