The most common tornado sound is a continuous rumble, like a closeby train. Sometimes a tornado produces a loud whooshing sound, like that of a waterfall or of open car windows while driving very fast. Tornadoes that are tearing through densely populated areas may be producing all kinds of loud noises at once, which collectively may make a tremendous roar. Just because you may have heard a loud roar during a damaging storm does not necessarily mean it was a tornado. Any intense thunderstorm wind can produce damage and cause a roar.
Tornadoes can last from several seconds to more than an hour.
Most tornadoes last less than 10 minutes. The details are still debated by tornado scientists. There are a lot of processes around a thunderstorm that can rob the area around a tornado of either instability or vorticity. Many tornadoes have been observed to go away soon after being hit by outflow. The irony is that some kinds of thunderstorm outflow may help to cause tornadoes, while other forms of outflow may kill tornadoes.