Many of the sounds we hear are periodic. When these sounds occur, vibrations repeat the same motion over and over again. One repetition of the vibration is called a cycle. Each cycle occurs over a consistent length of time called a period. Conceptually, a period is the time it takes for a signal to complete one cycle. To represent a signal’s period, we will use the greek letter tau, .
A related concept to period is a signal’s frequency, which is the number of cycles per second. Therefore, frequency is the inverse of period. To represent a signal’s frequency, we will use the letter, . The unit of frequency is called Hertz .
Below is a demonstration of different types of signals created from cyclical motion. In each case, the time it takes to complete a cycle (frequency) is the same. However, variations of the path for each cycle create different waveforms.