This is why you can still hear tire noise even when the car windows are closed. Tires, being the only part of the car that makes direct contact with the ground, serve several functions, one of which is reducing fuel consumption and noise.
1. Source of Tire Noise
Tire noise originates from the vibrations caused when the tire contacts the ground. The source of these vibrations can vary depending on the roughness of the road surface. For example, most everyday roads are rough, and these surfaces are a primary source of tire noise. On smooth, even asphalt, the design of the tire's tread, with its many patterns, causes vibrations that become the main source of noise.
There are mainly three types of vibrations that occur: vibrations from the tire structure, vibrations from the air in the internal cavities of the tire, and vibrations from the air trapped in the tire tread. These vibrations travel through two pathways to reach the ears, resulting in noise.
2.Paths of Noise Propagation
Structural Propagation: This refers to vibrations that cause various parts of the vehicle to vibrate, which then transmit to the interior of the car. Due to the vehicle parts' filtering effect on high-frequency vibrations, structural noise typically falls within the 20-800 Hz frequency range.
Airborne Propagation: This refers to vibrations that cause the surrounding air to move, with sound waves traveling directly to the ears. The frequency range for airborne noise is above 500 Hz, primarily concentrated in high frequencies above 800 Hz.
While these two pathways exist, they are not entirely independent. Noise may first propagate through the air and then transfer via structural vibration, entering the car and causing discomfort. In simple terms, this is why you can still hear tire noise with the windows closed.
3.Methods to Reduce Tire Noise
From a tire design perspective, reducing tire noise involves addressing two main factors.
Regarding the rubber compound, softer rubber generally provides better shock absorption, resulting in lower noise levels. However, this must be done while ensuring tire strength and durability.
Tread design is not only for drainage but also plays an important role in dry handling and noise control. Many tire manufacturers already have relatively mature products that reduce tire noise through tread arrangement, combined with adjustments in rubber formulas, resulting in the creation of quieter tires.
