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.
1. Engine has a rough idle. Your engine idles when it is a stationary and in this position the engine normally produces around 1000rpm. The sound the engine gives off is constant and smooth but if your spark plugs arenât performing as they should, your engine will produce a rough and jittery sound while producing larger vibrations through the car.