For nearly a decade, many car manufacturers, including Hyundai, have used technology called Active Sound Design (ASD) to give an engine a preset target sound. An ASD controller generates the vehicle engine’s sound based on various engine parameters, such as rpm, throttle and torque input. The ASD tool operates within an audio amplifier connected to the vehicle (see sidebar ‘How Active Sound Design usually works’). ASD also plays a key role in the South Korean automobile giant’s Personalized Engine Sound System.
“ASD allowed Hyundai’s Personalized Engine Sound System to be implemented originally, but it required a lot of on-road tuning of the designed sounds,” explains Wookeun Song, PhD, Research Engineer and key member of Brüel & Kjær’s Innovation Lab. “Somebody needs to be driving the prototype car, andsomebody else needs to be changing the settings. It’s not just a one-step design process; you have to do it iteratively, which makes it very time-consuming.”
Everything from different weather conditions to different road conditions have to be taken into account when tuning designed sounds. The repeatability of measurements can suffer with on-road tuning in prototype vehicles, due to changing background noise and operating conditions. And, it’s not possible to conduct back-to-back comparisons between different ASD amplifiers or between different tunings.
What’s more, demand for the prototype vehicles is huge. “The ASD designer, the door designer, the person setting up the amplifier... everyone wants to get access to this vehicle,” says Wookeun.
How ASD usually works
The physical properties of a vehicle’s engine and body normally determine the way it sounds inside the cabin. But ASD uses the vehicle’s audio system to enable users to experience a manufacturer preset ‘target’ sound instead. A standard CAN bus unit collects real-time driving information from the vehicle, then sends that information to the ASD controller. Based on that input and the loudspeaker transfer function (that is, how a sound created at a specific point sounds inside the cabin by the loudspeakers), the controller composes a configured engine sound, which it sends through the loudspeakers.