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.
#2. The sound you are probably hearing is straight-cut transmission. The whining noise is caused by the teeth of the gears slamming together. Its nothing to worry about and the reason why it's not audible in most road cars is that they use helical gears to keep the transmission whine to a minimum.