The natural frequency of an object depends on factors such as the elasticity and shape of the object. To make an object resonate, the frequency of the driving force has to match the natural frequency of the object. These spots are called dead spots. When two waves of slightly different frequencies overlap, their interference pattern is called beats. In the case of sound waves, we will hear periodic fluctuation in the loudness of sound when beats occur.
All sound waves travel at the same speed in the same medium.
Light travels much faster than sound in air, so you see a distant event much sooner than you hear it. The tremor in the ground can be felt before a distant explosion is heard because sound travels faster in the solid ground than in air.