Engineering Talk #9 Enhancing Sound

The sound a performance car makes is an integral part of its appeal and the Civic Type R was optimised for all conditions. 

The noise of an eager, rev-happy engine adds greatly to the enjoyment of driving a sports car but what is exciting on a race track can quickly become tiring on the highway, contributing to driver fatigue. Sports Sound engineer Osamu Matsuda was tasked with tuning the acoustics of the new Civic Type R for all possible applications, a powerful note on the race track yet reducing unnecessary noise and vibration when cruising.

This is a complex problem which has to take into account not only engine components and how they are mounted but also the exhaust itself and noise regulations in different countries around the world since the new Civic Type R is a global model.

Matsuda told us the goal of his project and his role within it, “My expertise is sound, mainly controlling vibration and noise. Vibration is an important issue for a car’s occupants, but not so for people outside the car. On the other hand, noise not only affects both occupants and people outside the car, but is regulated in each country, making it a complex matter.”

REDUCING VIBRATION

As a starting point Matsuda’s team carefully optimised the positioning and flexibility of the engine mounts to ensure it was highly rigid yet dampened vibrations. The engineers then looked at the amount and positioning of sound insulation materials before designing an exhaust silencer which would produce an authentically Type R noise both inside and outside the car.

However the team hit a snag when the engine development team changed a component as Matsuda explains, “The development team decided to reduce the weight of the flywheel, a component within the transmission, in order to improve engine response. This component rotates with the engine at high speeds, so even a minute change in weight slightly changes engine rev and noise volumes and frequencies. The new Type R was no exception, and we heard new sounds with the new flywheel. We overcame the new noise by slightly increasing the exhaust sound over the new rev range, managing to create a congruent sound overall.”

 

CLEVER TRICK

The small, central exhaust pipe of the Honda Civic Type R also offers an elegant solution to balancing the need for an exciting sound while accelerating or at the race track with a quiet, non-distracting noise while cruising at speed. When the Civic Type R accelerates, exhaust gases flow down the central pipe for a more aggressive note. Once at a steady cruise, back pressure causes the gases to be diverted through the larger exhaust pipes at either side, reducing noise levels and increasing refinement inside the car.