In this article, we visit a sound studio to learn how sound makes driving more fun. The sound being made here is not rock-n-roll or jazz, but the sound of tires. Bridgestone has an anechoic chamber at its tire development facility in Kodaira, Tokyo. Its walls, ceiling and floor are covered with sound-absorbing material. It is a special space that absorbs sound and prevents echoes. This is where tire sounds are re-created.
When a car is in motion, only part of the tire, about the size of a postcard, is in constant contact with the road. As the tire contacts the road surface, it makes a variety of sounds. These sounds vary according to the speed of the car and road conditions. In order to enhance quietness and comfort while driving and reduce stress caused by strange sounds, it is important in tire development to study the sounds made by tires. To this end, the anechoic chamber is an essential facility for research.
Bridgestone has two anechoic chambers. One of them measures the sound made by tires as they revolve. In this chamber, an environment is recreated that approximates driving conditions, and sounds are recorded by more than 100 microphones that change depending on pattern noise when the tire comes into contact with the road, and the type, shape and construction of materials. Data about how sounds change is analyzed to facilitate understanding.
In the other anechoic chamber, equipment measures the sounds made by air hitting the grooves in tires when a flat surface resembling a road is pressed against a stationary tire. The grooves in tires play a vital role in repelling water, but they are also a source of noise on dry roads, creating a phenomenon called columnar pipe resonance. This facility collects data about the sounds created by tire grooves, accounting for variances in the portion of the tire that comes into contact with the road surface at different speeds, vehicle weights and number of passengers.
Using these anechoic chambers, Bridgestone’s R&D has led to the creation of more pleasant tire sounds.
Related video: Performing a test in the anechoic chamber (from the 4 minutes 13 seconds point)
Bridgestone’s anechoic chamber