Damping

The damping is called a phenomenon that in an essentially oscillatory system, the amplitude of oscillation decreases with time or depending on the circumstances at all, no vibration occur. The oscillation is due after once supplied energy to the interaction of two forms of energy; For example, in a mechanical shaft kinetic energy and potential energy to be exchanged against each other. If this energy diverted into a third form of energy - often about as heat - so this is the cause of attenuation.

Furthermore, the term attenuation is applied to a weakening phenomenon which is related to vibration, radiation or wave-like processes; this characteristic physical quantities show but not necessarily a time- decaying, but quite steady state behavior. This process can proceed without time limit. Here energy is continuously supplied, and ultimately passed as heat.

• 2.1 basis parameters
• 2.2 Examples of attenuation 2.2.1 Electrical
• 2.2.2 optics
• 2.2.3 Acoustic

Time-dependent processes

Basis, characteristic

The attenuation may be undesirable, for example, in a movement that will vibrate indefinitely. But it may also be desirable, for example in an electromechanical measuring unit, which should quickly come to rest after a change of the measured variable.

In a damped oscillatory system distinguishes between resonant case Kriechfall and intervening aperiodic borderline case, but also has crawling behavior. Only at sufficiently weak damping vibration is at all possible. The mathematical representation is referred to the main article.

In the differential equation of the vibration damping is therein seen that a term using the first derivative of the dependent variables occurs. In mechanical processes this derivative is the rate of expression of an effect of friction.

For weak damping, the natural angular frequency of the oscillation is less than its value at undamped oscillation. The amplitude decays in an exponential relationship with time, so that the vibration through

Is writable. It is called with Abklingkoeffizient.

An oscillatory system with low damping ratio or high quality can be undamped driven by a temporally constant supply of energy (eg, mechanical or electrical tension ) as an oscillator. When excited with an alternating size resonance is possible. By inhibiting or dependent on the deflection (nonlinear ) damping must be prevented that the system until the destruction escalates (resonance catastrophe ).

Examples of attenuation

Mechanics

• A vibrating string are from over the body of a musical instrument energy, preferably by sound propagation.
• Vibrations in the chassis of vehicles are attenuated by shock; they become hot at high speed on bumpy trails. The attenuation is caused by friction braking condition, for example, a flow resistance due to viscosity when the oil is forced through narrow nozzles. For more options see also under vibration.

Electrical Engineering

• In a resonant circuit electric field and magnetic field share their energy. It primarily electric current gives energy to the ohmic resistance of the coil.
• In moving coil instrument, the conductive coil frame is used as an eddy current brake. It represents a turn in proportion to the angular velocity, a current flows as a result of electromagnetic induction.

Stationary processes

Basis, characteristics

Again, there are undesired and the desired damping. The latter requires an attenuator.

For components, pathways and systems are added to

• The damping factor

• The logarithmic damping ratio,

Of the (possibly complex ) variables and using each one whose magnitude is greater than one; thus, the amount is always a positive logarithm.

Examples of attenuation

Electrical Engineering

• Electromagnetic waves penetrate matter, subject to dielectric absorption when permanent electric dipoles are aligned by the polarization in the dielectric. This absorption leads to a conversion of energy from the alternating field in heat - both wanted to dielectric heating as well as unintentionally on the transmission paths of communication engineering. By damping the possible range is limited without amplification.

• Desired attenuators are also referred to as attenuator. In addition to components that are to be independent of frequency over a wide range as possible, are targeted frequency-dependent elements such as high-pass or low-pass in use.

• The shield is a technical measure to protect against electric, magnetic and electromagnetic fields. Their effectiveness is quantified by the shielding effectiveness.

For the attenuation of electromagnetic radiation as it passes through the atmosphere, see atmospheric window.

Optics

Also in the optics of the decadal or natural logarithm for identification is common

• For the weakening effect of filters: values ​​as optical density,
• Optical media: the absorption coefficient ( proportional to the imaginary part of the complex refractive index, that is the extinction coefficient ),
• In physical chemistry: the extinction coefficient.

Acoustics

In the different types of sound propagation of sound absorption may be required:

• Sound attenuation in reflection, a problem of room acoustics,
• The sound attenuation in transmission, such as walls, a problem of architectural acoustics.