信号与系统 | amplitude 与 magnitude 区别

注：本文为 “amplitude 与 magnitude” 相关文章合辑。

机翻，未校。

已对原文图片清晰度进行增强。

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FFT amplitude or magnitude

FFT 振幅还是幅度

Can I use the word amplitude instead of magnitude when I describe FFT bins? I don’t see any similar word in my language.
在描述 FFT 频段时，我可以用“amplitude（振幅）”这个词代替“magnitude（幅度）”吗？我在自己的语言里找不到类似的词。

Deve edited Mar 21, 2013 at 10:05

I’ve always considered them to be somewhat related, but different:
我一直认为它们有所关联，但又有所不同：

Amplitude is the peak value of a sinusoid in the time domain.
振幅是时域中正弦波的峰值。

Magnitude is the absolute value of any value, as opposed to its phase.
幅度是任何值的绝对值，与相位相对。

With these meanings, you would not use amplitude for FFT bins, you would use magnitude, since you are describing a single value. The link would be that for a pure sinusoid, the signal amplitude would be the same as the magnitude of the appropriate FFT bin (“same as” depending on what scaling etc is used in the FFT implementation, but at the very least will be “proportional to”).
基于这些含义，描述 FFT 频段时不会用“amplitude（振幅）”，而会用“magnitude（幅度）”，因为描述的是单个值。其联系在于，对于纯正弦波，信号振幅与相应 FFT 频段的幅度相同（“相同”取决于 FFT 实现中使用的缩放等因素，但至少是“成比例”的）。

In saying all that, if you were to tell me about the amplitude of an FFT bin, I would know exactly what you were talking about.
话虽如此，如果有人跟我讲 FFT 频段的振幅，我也完全能明白所指内容。

lxop answered Mar 21, 2013 at 20:14

Even I had confusion differentiating between these two terms at the beginning, have a look at this explanation from one of the Award-winning DSP books.
一开始我也对这两个术语的区别感到困惑，看看这本获奖的数字信号处理（DSP）书籍中的解释吧。

Amplitudes

振幅

Magnitudes

幅度

Sufiyan Ghori answered Mar 21, 2013 at 13:53

Just because one book defines it that way doesn’t mean it’s standard among engineers.
仅仅一本书这样定义，并不意味着这就是工程师们通用的标准。

– endolith Commented Mar 28, 2013 at 19:52

Which book is this from?
这出自哪本书？

– sourcenouveau Commented Mar 23, 2015 at 13:50

@M.Dudley // Not sure, but probably it’s from Oppenheim’s book I learnt.
@M.Dudley // 不确定，但可能是我学过的奥本海姆的书。

• Digital Signal Processing: Oppenheim, Alan V.: Trade Paperback: 9780132146357
  <https://www.powells.com/book/digital-signal-processing-9780132146357>

– Youngjae Commented Sep 7, 2016 at 1:11

@M.Dudley I just happened to come across this post while reading this exact book. It’s from Chapter 1 (section 1.2) in “Understanding Digital Signal Processing” by Richard G. Lyons.

@M.Dudley 我刚好在读这本书时看到了这篇文章。它来自 Richard G. Lyons 所著的《理解数字信号处理》第 1 章（1.2 节）。

– tjwrona Commented Jun 29, 2019 at 17:30

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Difference Between Magnitude and Amplitude

幅度与振幅的区别

Magnitude and amplitude are frequently used interchangeably to describe characteristics of numbers in common parlance. Both words are interchangeable, according to a thesaurus. Yet in engineering, they signify two distinct things, therefore it’s crucial to know the difference.
在日常用语中，“Magnitude（幅度）”和“Amplitude（振幅）”常被互换使用来描述数字的特征。根据同义词词典，这两个词可以互换。然而在工程领域，它们代表着两种截然不同的概念，因此了解它们的区别至关重要。

The maximum positive or negative value to which a variable deviates from its mean is referred to as its amplitude. It is just the farthest a vibration or oscillation may go from its stable location (zero level). Because of this, signal amplitudes can either be positive or negative.
振幅指的是变量偏离其平均值的最大正值或负值。它仅仅是振动或振荡可能偏离其稳定位置（零电平）的最远距离。正因如此，信号的振幅可以是正值，也可以是负值。

On the other hand, a variable’s magnitude is a measurement of how much its amount deviates from zero in any direction. As a result, magnitudes are always positive.
另一方面，变量的幅度是对其在任何方向上偏离零的程度的度量。所以，幅度总是正值。

What is Amplitude?

什么是振幅？

Amplitude refers to the maximum displacement of a wave from its equilibrium position. It is a measure of the strength or intensity of a wave. Amplitude is usually represented by the letter A and is expressed in units of distance. For instance, in a sound wave, the amplitude can be used to describe the loudness of the sound.
振幅是指波从其平衡位置的最大位移。它是衡量波的强度或烈度的指标。振幅通常用字母 A 表示，并以距离单位来度量。例如，在声波中，振幅可用来描述声音的响度。

What is Magnitude?

什么是幅度？

Magnitude refers to the distance or quantity of a variable, regardless of its direction. In physics, the distance and the direction between two points can be represented by a quantity known as a vector.
幅度是指变量的距离或数量，不考虑其方向。在物理学中，两点之间的距离和方向可以用一个称为向量的量来表示。

Magnitude is the length of the vector, while direction simply is a way from point A to point B. By contrast, quantities known as scalar quantities only have magnitude, so they can be described using just a real number. The magnitude of a scalar quantity is a scalar.
幅度是向量的长度，而方向仅仅是从 A 点到 B 点的路径。相比之下，被称为标量的量只有大小，因此可以仅用一个实数来描述。标量的幅度就是标量本身。

Magnitude refers to the size of an object, which determines whether one object is larger or smaller than the other object. If you talk about magnitude of some object, you simply refer to its size or scale. For example, the magnitude of a football is greater than that of a tennis ball or a golf ball for that matter. Magnitude is used to measure the extent of an earthquake or an explosion.
幅度还用于描述物体的大小，它决定了一个物体比另一个物体大还是小。当提及某个物体的幅度时，仅仅是指它的大小或规模。例如，足球的大小大于网球或高尔夫球。幅度还用于衡量地震或爆炸的强度。

Applications of Magnitude and Amplitude

幅度与振幅的应用

Magnitude and amplitude have various applications in different fields. In physics, magnitude is used to describe the strength or intensity of a physical quantity. For example, in electrostatics, the magnitude of the electric field strength is used to describe the force exerted on a charged particle.
幅度和振幅在不同领域有多种应用。在物理学中，幅度用于描述物理量的强度或大小。例如，在静电学中，电场强度的幅度用于描述施加在带电粒子上的力。

In contrast, amplitude is used to describe the intensity or strength of a wave. For instance, in the study of sound waves, the amplitude is used to describe the loudness of a sound. In electromagnetic waves, such as light waves, the amplitude can be used to describe the brightness of the light.
相比之下，振幅用于描述波的强度或大小。例如，在研究声波时，振幅用于描述声音的响度。在电磁波（如光波）中，振幅可用于描述光的亮度。

Moreover, amplitude is also used in the field of signal processing. In this field, amplitude is used to describe the strength of a signal. This information can be used to filter out noise from a signal or to amplify a weak signal.
此外，振幅在信号处理领域也有应用。在这个领域，振幅用于描述信号的强度。这些信息可用于滤除信号中的噪声或放大微弱信号。

Differences: Magnitude and Amplitude

幅度与振幅的差异

The main difference between magnitude and amplitude is that magnitude refers to the size or amount of a physical quantity, while amplitude refers to the strength or intensity of a wave. Magnitude is a scalar quantity that can be positive, negative, or zero, while amplitude is a vector quantity that has both magnitude and direction.
幅度和振幅的主要区别在于，幅度指的是物理量的大小或数量，而振幅指的是波的强度或大小。幅度是一个标量，可以是正值、负值或零，而振幅是一个矢量，既有大小又有方向。

Another difference between magnitude and amplitude is the way they are measured. Magnitude is measured using different units depending on the physical quantity being measured. For example, distance can be measured in meters, speed in meters per second, and force in Newtons. Amplitude, on the other hand, is measured in units of distance, such as meters, millimeters, or micrometers.
幅度和振幅的另一个区别在于它们的测量方式。幅度根据所测量的物理量使用不同的单位来度量。例如，距离可以用米来测量，速度用米每秒来测量，力用牛顿来测量。而振幅则以距离单位来测量，如米、毫米或微米。

The following table highlights the major differences between Amplitude and Magnitude −