1. (Units) a unit of heat in the fps system equal to the quantity of heat required to raise the temperature of 1 pound of water by 1Â°F. 1 British thermal unit is equivalent to 1055.06 joules or 251.997 calories.
Quick Answer. A major factor that usually causes tire noise is the air chamber inside the tire. The large void that is filled with air acts as a giant resonance chamber. Thus, the tires are something like donut-shaped drums that generate a low-frequency hum when tires are rolling.
Other Noise Sources. Not all tire noise is due to the design of the tread pattern. Tires also make noise because the tread elements squirm under the weight of the car and slip over the pavement. At low speeds, some of the easiest places to observe this type of noise are parking garages with polished concrete floors.