Ford Focus ST Features Active Sound Symposer
Ford engineers have added a new twist to the existing technology of the Focus ST so that the engines not only sing but also roar at the same time. A sound symposer – a special sound tube – amplifies the throat frequencies craved by enthusiasts in performance of cars. The engineers worked to naturally amplify the lower range of engine frequencies found between 200 and 450 Hz.
The Mustang features the sound tube concept, but the sound symposer used in Focus ST is unique because of its electronically controlled valve that opens and closes based on driver inputs – engine speed, accelerator pedal position and gear selection. The valve is mapped more aggressively in lower gears but in higher ones it is quieter. In Focus ST, the symposer is attached directly to the intake manifold. “For ST drivers, it’s not enough to have a car that is fast or feels fast. It also has to sound fast,” says Christopher Myers, Air Induction System engineer. “Part of this is the design of the exhaust, but we went further and engineered the symposer both to dial up the nice sounds the EcoBoost delivers under the hood but dial back the interior sound volumes at part throttle.”
An international team from suppliers of the intake manifold, battery tray, electrical hardware and software, and electrical connectors came together with Ford to accelerate development of the symposer. “The sound symposer gives the Focus ST an aural split personality,” says Lisa Schoder, Ford Focus ST Marketing manager. “In everyday driving, the car is composed and refined. But under full throttle, we unleash the sonic hounds. It’s a beauty and a beast.”