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.
I noticed recently that there is a humming or growling noise coming from the driver's front wheel area that increases(higher pitch) with speed. It makes the noise when slowing down also. There is no noise at idle or parking lot speed. The noise started as slightly audible and has increased to being heard over the radio.