2 The Kinematics of Vibration and Acoustics

The motion represented by the equation or, in more compact complex variable notation, is called simple harmonic motion. Most vibrations and noise we encounter belong to the category of linear vibration and consist of a linear combination of simple harmonic motions of different amplitudes, frequencies and phases. The frequency of a point mass-spring system is given by: The frequency in cycles/s, or Hz, is related to the frequency in radians/s by, The instantaneous velocity and acceleration of a vibrating point mass is given by: The velocity of propagation of a wave is given by: Vibrations can be represented in the time domain (time histories) or in the frequency domain (power spectral densities). Both contain the same information.