In this blog post, we’ll explore various technologies for controlling car noise, as well as the principles and future directions of the latest technologies designed to transform unpleasant sounds into pleasant ones.
“Vroom, vroom.” When walking along the roadside, it’s natural to frown at the noise emitted by countless cars. In fact, on roads with heavy traffic, it’s often difficult to even hold a conversation with the person next to you. This noise goes beyond mere inconvenience; it causes psychological stress and has a negative impact on health. Research findings consistently show that prolonged exposure to excessively high noise levels can lead not only to hearing loss but also to cardiovascular diseases and sleep disorders. In major cities, in particular, persistent noise pollution is identified as a major factor degrading citizens’ quality of life. Consequently, the issue of noise is recognized as a critical challenge that must be addressed not merely as a daily inconvenience, but at the societal and public health levels.
Noise remains a significant problem even when riding in a car. Noise entering the vehicle’s interior continuously stimulates passengers’ ears, increasing fatigue and making them more irritable, which can impair concentration while driving. Particularly during long drives, this noise can accelerate the buildup of fatigue, thereby increasing the risk of accidents. For this reason, effectively controlling automotive noise is one of the key criteria determining a vehicle’s comfort and ride quality. On a societal level, noise emission standards for vehicles are continuously regulated to minimize the harm caused by noise, and automakers are researching and developing various noise-reduction technologies to provide a more pleasant driving environment. So, how is automotive noise currently being controlled?
Imagine loud music playing in a corner of a room. If there were no barriers between the speaker and you, the loud sound would reach your ears directly, causing discomfort. So, how can this noise be reduced? First, you could surround the speaker with thick walls. Thick walls block the transmission of sound between the speaker and the listener, making the loud music sound much quieter. Another method is to generate a different sound that can cancel out the original sound. Since sound consists of waves with a specific frequency and waveform, generating a sound with the same frequency but opposite phase causes the two sounds to interfere with each other, significantly reducing the overall volume. This is called sound cancellation. The final method is very simple: simply lowering the volume of the music playing from the speaker.
Noise generated by cars can also be understood using the same principle. Automotive noise is primarily generated during the operation of the powertrain; in internal combustion engine vehicles, the engine and exhaust system are the main sources. While electric vehicles produce almost no engine noise, the motor, transmission, friction between tires and the road surface, and aerodynamic noise generated between the vehicle body and the air are the primary sources of noise. If a vehicle lacks devices to reduce these noises, the generated noise is transmitted directly into the cabin, interfering with driving. To mitigate this, sound-absorbing and sound-insulating materials are strategically placed inside the vehicle body. These materials absorb, reflect, or block the sounds generated by the vehicle, significantly reducing the noise transmitted into the cabin. Automakers are continuously advancing these technologies; in particular, luxury vehicles employ increasingly sophisticated sound-absorption and sound-insulation techniques to provide an even quieter and more comfortable cabin environment.
Next is Active Noise Control (ANC) technology, which actively reduces noise inside the vehicle. This system uses microphones installed in the cabin to measure noise in real time, and the vehicle’s audio speakers then generate sound waves of opposite phase to cancel out the noise. Recently, this technology has been widely adopted in various passenger vehicles, including electric and hybrid cars, and techniques to optimize control performance in real time based on vehicle speed and driving conditions are also advancing. Finally, to reduce noise at its source, manufacturers improve the materials or shapes of noise-generating components. A prime example is the tire. Optimizing the tire tread pattern or incorporating sound-absorbing materials inside the tire can effectively reduce noise generated by friction with the road surface. Additionally, technologies that reduce vibration and noise by improving the motor, transmission, suspension, and body structure are continuously advancing.
Recently, sound design technology has advanced beyond simply reducing noise to designing the interior acoustics so that occupants feel more comfortable. As a result, cars are evolving from merely “quiet cars” to “cars that sound good.”
