常用振動名詞術語的英文解釋,加強對概念的理解

振動：The oscillatory (back and forth) motion of a physical object.

噪聲：Any component of a transducer signal which does not represent the variable intended to be measured.

固有頻率(振動中最重要的概念)：The frequency of free vibration of a mechanical system at which a specific natural mode of the system elements assumes its maximum amplitude.

強迫振動：The response vibration of a mechanical system due to a forcing function (exciting force). Typically, forced vibration has the same frequency as that of the exciting force.

自由振動：Vibration response of a mechanical system following an impulse like initial perturbation (change of position, velocity or external force). Depending on the kind of perturbation, the mechanical system responds with free vibrations at one or more of its natural frequencies.

絕對振動：Vibration of an object as measured relative to an inertial (fixed) reference frame. Accelerometers and velocity transducers measure absolute vibration typically of machine housings or structures; thus they are referred to as seismic transducers or inertial transducers.

簡諧振動：Sinusoidal vibration with a single frequency component.

赫茲：(Hz) Unit of frequency measurement in cycles per second.

頻率：The repetition rate of a periodic vibration per unit of time. Vibration frequency is typically expressed in units of cycles per second (Hertz) or cycles per minute (to more easily relate to shaft rotative speed frequency). In fact, since many common machine malfunctions produce vibration which has a fixed relationship to shaft rotative speed, vibration frequency is often expressed as a function of shaft rotative speed. 1X is a vibration with a frequency equal to shaft rpm, 2X vibration is at twice shaft rpm, 0.5X vibration with a frequency equal to one-half shaft rpm, etc.

振幅：The magnitude of periodic dynamic motion (vibration). Amplitude is typically expressed in terms of signal level, e.g., millivolts or milliamps, or the engineering units of the measured variable, e.g., mils, micrometres (for displacement), inches per second (for velocity), etc. The amplitude of a signal can be measured in terms of peak to peak, zero to peak, root mean square, or average.

相位角：The timing relationship, in degrees, between two vibration signals, such as a Keyphasor® pulse and a vibration signal; also, the phase difference between two signals, such as the input force signal and output response signal. The "lag" corresponds to "minus" in mathematical formulations.

加速度：The time rate of change of velocity. For harmonic motion, this is often expressed as g or a. Typical units for acceleration are feet per second per second (ft/s2) pk, meters per second per second (m/s2) pk, or more commonly g pk (= acceleration of earths gravity = 386.1 in/s2 = 32.17 ft/s2 = 9.81 m/s2). 

Acceleration measurements are generally made with an accelerometer and are typically used to evaluate high frequency vibration of a machine casing or bearing housing due to blade passing, gear mesh, cavitation, rolling element bearing defects, etc.

速度：The time rate of change of displacement. Typical units for velocity are inches/second or millimetres/second, zero to peak. Velocity measurements are used to evaluate machine housing and other structural response characteristics. 

Electronic integration of a velocity signal yields displacement, but not position.

位移：The change in distance or position of an object relative to a reference. Machinery vibration displacement is typically a peak to peak measurement of the observed vibrational motion or position, and is usually expressed in units of mils or micrometres. Proximity probes measure displacement directly. Signal integration is required to convert a velocity signal to displacement, but does not provide the initial displacement (distance from a reference) measurement.

分貝：A numerical expression of the ratio of the power or voltage levels of electrical signals.

dB = 10 log P1/P2 = 20 log V1/V2.

共振：The condition in which the frequency of an external force coincides with a natural frequency of the system. A resonance typically is identified by an amplitude peak, accompanied by a maximum rate of change of phase lag angle.

頻譜：Commonly a presentation of the amplitudes of a signal's frequency components versus their frequencies. Or the frequency content of a signal.

信噪比：The number formed by dividing the magnitude of the signal by the magnitude of the noise present in the signal. A low noise signal has a high Signal-to-Noise Ratio, while a high noise signal has a low Signal-to-Noise Ratio. The noise can originate from many different sources and is considered to be any part of the signal which does not represent the parameter being measured.

聲明：本文根據聲振論壇會員NASA轉發於聲振論壇的相關資料編輯而成。