Various environments and technologies surrounding automobiles are changing drastically, such as a shift to Electric Vehicles (EV) and autonomous driving becoming a reality.
To provide a comfortable space inside the vehicle with greater silence, Toyo Tires has developed a new device that effectively reduces resonance in tire cavities (tire cavity noise), which is one source of vehicle interior noise.
The noise heard when driving a car includes airborne ( = pattern noise), which is sound generated from the contact area between the road surface and the tire tread that is transmitted through the air, and structure-borne ( = road noise), which is caused by tire vibrations that is transmitted to the interior of the vehicle via the vehicle axles.
“Tire cavity noise,” or the noise generated by the transmission of resonance phenomenon of the air inside the tire
Tire cavity noise is firstly triggered by tire vibration on road surface.
This vibration then causes the air inside the tire to vibrate = sound.
As a result, interior noise is generated when the air inside the tire resonates and is transmitted into the vehicle.
An uncomfortable noise that occurs in a specific band
Tire cavity noise is one of the interior noises that is generated in the frequency range of approximately 200-250 Hz, depending on tire sizes.
Such as, the bumping sound heard when driving over seams, or the noise heard when driving on rough roads.
Visualization of status of air inside tire which causes noise when vehicles are traveling
Through these visualizations, we have confirmed that air itself has generated “flow in the circumferential direction,” and “flow in the vertical (radial) direction” inside tire.
Device developed using our unique approach to reduce noise by utilizing the flow of air
In addition to the conventional method, Toyo Tires has focused on the fact that air flow is generated inside tire, and incorporated its unique approach to reduce noise by utilizing flow of air inside tire.
Noise reduction has been realized by utilizing the flow of air inside tire. The device has a unique structure combining arch-shaped perforated film and cylindrical foam.
Noise is reduced when passing through the pores.
a) Because friction is generated at the wall faces of the pore when air passes through, the energy of the sound is reduced.
b) Because the sound passed through becomes a vortex, the energy of the sound is reduced.
By utilizing these two mechanisms, noise is reduced by allowing the sound inside tire to pass through the pores in the perforated film.
The arch shape of the perforated film is critical to the noise reduction.
The structure of the perforated film arranged in an arch shape is confirmed to be effective towards noise reduction using air flow inside tire in both circumferential and radial directions.
By arranging hollow-structured cylindrical foam that has a noise-reducing effect, further noise reduction and the arch shape of perforated film is maintained.
In addition to the perforated film, cylindrical foam is arranged, which creates a noise-reducing effect due to its hollow structure.
Because of this, the perforated film maintains the arch shape, which catches the flow of air in both circumferential and radial directions.
The synergistic effect between the perforated film and cylindrical foam further enhances their noise reduction effect.
The arch shape of the perforated film is critical to the noise reduction.
The structure of the perforated film arranged in an arch shape is confirmed to be effective towards noise reduction using air flow inside tire in both circumferential and radial directions.
6-11% noise reduction across the entire range achieved inside the vehicle
We have confirmed the possibility of noise reduction of 6-11% in noise level inside the vehicle across the entire range (even outside the frequency band of tire cavity noise band, 200-250 Hz).
This was especially effective in middle and rear seats.
We will continue to evolve tires through the use of technology while continuing our efforts to attain unique technical innovations to develop products required by the next generation of mobility society.
More awesome promotion and latest news and events waiting for you. Stay tuned.
