To some powertrain aficionados, the sound of a whistling turbocharger pushing air through a small-displacement 4-cyl. engine is merely an unpleasant whine.

Mann+Hummel USA Inc. has a new product to cancel out that turbo whine — at least for the driver. At the World Congress, the German supplier exhibited a compact, lightweight component soon to be marketed as the “symposer.”

The purely mechanical device, made up of four chambers, attaches directly in front of the throttle body. A movable flap senses pulsations generated when the engine vibrates due to acceleration.

As the flap moves, via a spring-mass system, it changes the high-frequency whistle of the turbocharger to the more muscular tone that is the natural byproduct of the combustion process.

That sound is carried through the outlet chambers of the symposer through the partition wall into the passenger compartment, through a sound pipe.

“You can attenuate the sound and make your engine sound like a throaty, high-performance V-6,” Mann+Hummel's John Baumann says. The supplier collaborated with Ford Motor Co. and DaimlerChrysler AG in developing the symposer.

Baumann declines to attach a price to the technology but says it costs significantly less than electronically controlled active noise-cancellation devices currently available.

This year, the symposer is standard on the ST sport version of the Ford Focus in Europe, powered by a 2.5L 5-cyl. turbocharged gasoline engine from Volvo Cars.

Mann+Hummel also demonstrates a hydrocarbon trap that meets California Air Resources Board requirements for partial zero emission vehicles.