A fourth property of sound, its phase, is less directly related to how sound is heard. Phase is important in describing how complex sounds can be constructed from the simple sinusoidal waves. Below is an example of two sound waves with the same frequency and amplitude - only their alignment with respect to time differs. By specifying amplitude, wavelength, and phase, any sinusoid can be exactly described. By describing these parameters for all frequency components, any complex signal can be described exactly.