When the new Ford Focus ST accelerates, it’s nowhere near as noisy as expected due largely to the device called the “active sound symposer.” Automakers always aim find the balance between sound and sight, just like what the Ford Focus ST has achieved. The symposer has the appearance of a sound tube that was formerly used on cars like the Mustang.
It’s more advanced but it works the same way of pumping sound from the engine to the interior. It is directly attached to the intake manifold and pipes in a particular frequency range (200 to 450 Hz) into the cabin. The symposer comes with an electronically-controlled valve that opens and closes according to several factors such as the engine speed, throttle position, and gear selection.
The valve is intended to be more aggressive in lower gears and more passive in higher gears for quieter freeway cruising, which means that it celebrates the best of both worlds. The Focus ST has a 2.0-liter EcoBoost turbo-four, which produces 252 hp and 270 lb-ft of torque.
But even with this high performance, it offers a pleasant muscular baritone soundtrack due partly to the symposer. “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."