What are the Units of Vibration? 

Introduction

Vibration is not considered a physical quantity. So it does not have a standard unit. It is a type of complex signal that represents an object’s state at different frequencies and various amplitudes. When elastic bodies such as a spring or a shaft are displaced from their equilibrium position by the application of external forces, they execute the vibratory motion. Vibratory motions are observed in our daily lives. For example: In humans, the vocal cords vibrate when they speak, the strings of a guitar vibrate when struck, etc.,

Overview of Vibration

In physics, vibration refers to the periodic to and fro of the particles of an elastic body or a medium, from its point of equilibrium. It can also be defined as any motion that repeats itself after some time. It means that the time taken to complete one cycle of vibration is always the same. Everything in nature vibrates at a different frequency. The vibrating object is the source of the disturbance caused that travels through a medium. Any object that is plucked, shaken, struck or disturbed from its equilibrium position will vibrate.

Different Units of Vibration

Many factors are considered while deriving the units of vibration depending on their properties:-

1. Frequency: It is defined as the number of times the motion by a vibrating object was repeated in one second. It is denoted as f and the unit of frequency is Hertz (Hz).
2. Displacement: It is referred to as the distance between the peaks of vibration or the distance covered by the vibrating object from a fixed position. It is denoted as d and the units of displacement will be m, mm, μm.
3. Velocity: It is defined as the maximum speed attained by the vibrating object. It also means the changing rate of displacement per unit of time. It is denoted as v and the units of velocity will be m/s, and cm/s.
4. Acceleration: It refers to a measure of how quickly speed changes with time. It is defined as the rate at which velocity changes per unit of time. It is denoted as a and the units of acceleration will be m/s2, cm/s2, mm/s2 and g.
5. Other units: Vibration when measured as sound, will have Watts per meter square (W/m2) as the measuring unit.

 Classification of Vibration

1. Free or natural vibration: The vibrations occurring in an elastic body or medium when no external force acts on it are called free or natural vibrations. The frequency at which the free vibration occurs is known as natural frequency. For example oscillations of a simple pendulum.
2. Forced vibration: When the body or an object vibrates due to an external force applied to it, then the body is said to be executing forced vibration. For example, the vibration of a moving vehicle plucked strings of a veena or a sitar, etc.,
3. Damped vibration: When the vibrations in the body or the medium are diminishing with every cycle of vibration due to experiencing any friction or resistance, then such a vibration is known as damped vibration. For example, when a thin branch of a tree is pulled and released, the diving board in the swimming pool gradually ceases to oscillate after the diver has jumped off the board, etc.,

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