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A term broadly used to denote either the dissipation of energy in, and the consequent decay of, oscillations of all types or the extent of the dissipation and decay. The energy losses arise from frictional (or analogous) forces which are unavoidable in any system or from the radiation of energy to space or to other systems. For sufficiently small oscillations, the analogous forces are proportional to the velocity of the vibrating member and oppositely directed thereto; the ratio of force to velocity is -R, the mechanical resistance. For the role of damping in the case of forced oscillations, where it is decisive for the frequency response, See Forced oscillation, Resonance (acoustics and mechanics), Harmonic motion, Oscillation, Vibration

An undamped system of mass m and stiffness s oscillates at an angular frequency &ogr;0 = (s/m)1/2. The effect of a mechanical resistance R is twofold: It produces a change in the frequency of oscillation, and it causes the oscillations to decay with time. If u is one of the oscillating quantities (displacement, velocity, acceleration) of amplitude A, then Eq. (1) holds in the damped case, whereas in the undamped case Eq. (2)

holds. The reciprocal time 1/α in Eq. (1) may be called the damping constant.

The damped angular frequency ωd in Eq. (1) is always less than ω0. According to Eq. (1), the amplitude of the oscillation decays exponentially; the time required for the amplitude to decrease to the fraction 1/e of its initial value is equal to 1/α.

A common measure of the damping is the logarithmic decrement δ, defined as the natural logarithm of the ratio of two successive maxima of the decaying sinusoid. If T is the period of the oscillation, then Eq. (3) holds. Then 1/δ is the number

of cycles required for the amplitude to decrease by the factor 1/e in the same way that 1/α is the time required.

The Q of a system is a measure of damping usually defined from energy considerations. The Q is π times the ratio of peak energy stored to energy dissipated per cycle and is equal to π/δ.

If α in Eq. (1) exceeds ω0, then the system is not oscillatory and is said to be overdamped. If the mass is displaced, it returns to its equilibrium position without overshoot, and the return is slower as the ratio α/ω0 increases. If α = ω0 (that is, Q = 1/2), the oscillator is critically damped. In this case, the motion is again nonoscillatory, but the return to equilibrium is faster than for any overdamped case.


Reducing or eliminating reverberation in a room by placing sound-absorbing materials on the walls and ceiling. Also known as soundproofing.
The dissipation of energy in motion of any type, especially oscillatory motion and the consequent reduction or decay of the motion.
The extent of such dissipation and decay.


The dissipation of energy with time, e.g., the dissipation of energy in a mechanical system whose free oscillations decrease with time, resulting in a decrease in its amplitude of vibration.


A technique for stabilizing an electronic or mechanical device by eliminating unwanted or excessive oscillations.
References in periodicals archive ?
05) the percent seedling survival, decreased damping off severity, increased crop stand, and increased both quality and quantity of yield as compared to flat beds (Table 1).
Damping off is that maddening fungal infection that makes seedlings wilt and die just as you thought you'd succeeded.
And when you do, you're far less likely to get fungal infections on plants such as damping off.
The seedlings are subject to damping off and larger plants, under glass, are subject to the usual pests such as red spider mite and whitefly.
5Keep the greenhouse fan going where late-flowering chrysanthemums are coming into bloom to prevent damping off.
Please can you tell me how to avoid the seedlings collapsing with damping off disease?
A MOST of the dirt and potential sources of infection from diseases such as damping off can be removed if you scrub all your pots and trays thoroughly with a stiff brush and warm soapy water.
AFTER pricking out seedlings always water them in well with mains water or for added protection against damping off use a solution of Cheshunt Compound.
Always use mains water - if the water is collected from a water butt it can cause damping off.
Ensure the seeds are not kept too moist once in the compost and sow them fairly thinly to reduce the risk of damping off.
After transplanting seedlings or pricking them out, water the compost with a suitable copper-based fungicide to greatly reduce the risk of damping off diseases developing.
CONTINUE to prick out seedlings of flowers and vegetables sown last month, watering them in with a copper fungicide to prevent damping off.