Which is the best description of the cause of sound waves?
a.a decrease in pressure
b.one object bumping into another
c.molecules becoming electrically charged
d. a vibration in material causing a vibration in an adjacent area
When we hear something, we are sensing the vibrations in the air. The number of vibrations per second is known as the frequency, measured in Hertz (1 Hz = 1 vibration per second).
