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.
Excessive backlash in the differential gears, or worn bearings or gears in the transmission or transaxle will typically make a whining noise thatâs loudest during deceleration, but rarely cause a vibration. If you detect audible gear noise, check the lube levels in the differential, transmission or transaxle.