Vibration

Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point.

The term vibration is precisely used to describe mechanical oscillation.

In many cases, however, vibration is undesirable, wasting energy and creating unwanted sound.

In physics, sound is a vibration that typically propagates as an audible wave of pressure, through a transmission medium such as a gas, liquid or solid.

Sound, or pressure waves, are generated by vibrating structures (e.g. vocal cords); these pressure waves can also induce the vibration of structures (e.g. ear drum).

They vibrate, modulating the flow of air being expelled from the lungs during phonation.

The measured response may be ability to function in the vibration environment, fatigue life, resonant frequencies or squeak and rattle sound output (NVH).

Many problems are generated as either vibration or noise, transmitted via a variety of paths, and then radiated acoustically into the cabin.

Vibration can be desirable: for example, the motion of a tuning fork, the reed in a woodwind instrument or harmonica, a mobile phone, or the cone of a loudspeaker.

A reed made from a piece of warped tube cane won't vibrate consistently on both sides, affecting the sound.

The mechanical system vibrates at one or more of its natural frequencies and damps down to motionlessness.

Mechanical resonance is the tendency of a mechanical system to absorb more energy when the frequency of its oscillations matches the system's natural frequency of vibration than it does at other frequencies.

Devices specifically designed to trace or record vibrations are called vibroscopes.

Vibroscope (vibrare 'vibrate' + scope) is an instrument for observing and tracing (and sometimes recording) vibration.

Note: angular frequency ω (ω=2 π f) with the units of radians per second is often used in equations because it simplifies the equations, but is normally converted to ordinary frequency (units of Hz or equivalently cycles per second) when stating the frequency of a system.

Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light.

This phenomenon is called resonance (subsequently the natural frequency of a system is often referred to as the resonant frequency).

Mechanical resonance is the tendency of a mechanical system to respond at greater amplitude when the frequency of its oscillations matches the system's natural frequency of vibration (its resonance frequency or resonant frequency) than it does at other frequencies.

Vibration isolation is the process of isolating an object, such as a piece of equipment, from the source of vibrations.

VA is a key component of a condition monitoring (CM) program, and is often referred to as predictive maintenance (PdM).

The most commonly used method for rotating machines is vibration analysis.

VA is a key component of a condition monitoring (CM) program, and is often referred to as predictive maintenance (PdM).

To evaluate equipment condition, predictive maintenance utilizes nondestructive testing technologies such as infrared, acoustic (partial discharge and airborne ultrasonic), corona detection, vibration analysis, sound level measurements, oil analysis, and other specific online tests.

In rotor bearing systems any rotational speed that excites a resonant frequency is referred to as a critical speed.

As the speed of rotation approaches the object's natural frequency, the object begins to resonate, which dramatically increases system vibration.

This is referred to an eigenvalue problem in mathematics and can be put in the standard format by pre-multiplying the equation by

Originally utilized to study principal axes of the rotational motion of rigid bodies, eigenvalues and eigenvectors have a wide range of applications, for example in stability analysis, vibration analysis, atomic orbitals, facial recognition, and matrix diagonalization.

Vibration and impact shock during shipment and loading/unloading are controlled by cushioning to reduce the chance of product damage.

The steady state solution of this problem can be written as:

This is often observed in vibrating systems, such as a clock pendulum, but can happen with any type of stable or semi-stable dynamic system.

Pallesthesia (\ˌpal-es-ˈthē-zh, or vibratory sensation, is the ability to perceive vibration.

The methods to handle the related problems are similar, to a certain level, where most shipboard noise problems are reduced by controlling vibration.

and to dampen vibrations in fabricated structures like machine beds and housings.

A tuned mass damper (TMD), also known as a harmonic absorber or seismic damper, is a device mounted in structures to reduce the amplitude of mechanical vibrations.

Torsional vibration is angular vibration of an object—commonly a shaft along its axis of rotation.

A shock data logger or vibration data logger is a measurement instrument that is capable of autonomously recording shocks or vibrations over a defined period of time.

H(i\omega) is called the frequency response function (also referred to as the transfer function, but not technically as accurate) and has both a magnitude and phase component (if represented as a complex number, a real and imaginary component).

Complex numbers have applications in many scientific areas, including signal processing, control theory, electromagnetism, fluid dynamics, quantum mechanics, cartography, and vibration analysis.

An example of animating mode shapes is shown in the figure below for a cantilevered I-beam as demonstrated using modal analysis on ANSYS.

An example of animating mode shapes is shown in the figure below for a cantilevered I-beam as demonstrated using modal analysis on ANSYS. This technique is used in the field of experimental modal analysis to determine the vibration characteristics of a structure.

Although modal analysis is usually carried out by computers, it is possible to hand-calculate the period of vibration of any high-rise building through idealization as a fixed-ended cantilever with lumped masses.