动态范围压缩如何改变音频？
Dynamic Range Compression is used in everything. Most audio editors have a “compressor effect,” and mastering it can mean the difference between an amateur and pro-level mix. To understand how it works, we need to see what exactly it does.
动态范围压缩可用于所有方面。 大多数音频编辑器都有“压缩器效果”，掌握它可能意味着业余和专业级混音之间的区别。 要了解它是如何工作的，我们需要查看它的确切作用。
动态范围压缩 (Dynamic Range Compression)
First of all, this should not be confused with general “audio compression,” which is data compression and covers things like MP3 conversion. We’re most definitely NOT talking about compression of quality for space-saving reasons. If that’s what you’re looking for, check out HTG Explains: What Are the Differences Between All Those Audio Formats?
首先，不要将其与一般的“音频压缩”相混淆，后者是数据压缩，涵盖了MP3转换之类的内容。 出于节省空间的原因，我们绝对不是在谈论质量压缩。 如果您要寻找的是，请查看HTG解释：所有这些音频格式之间有什么区别？
We are talking about compression of the dynamic range of sound in an audio track. If you record a pin-drop followed by a TNT explosion, you’ll notice that there’s a very large difference in the intensities of those two sounds. That’s what we refer to as dynamic range. Now, our ears are pretty good at working with large differences like that, but audio equipment isn’t. If you ever watched a war movie where the actors’ dialogue was drowned out by gunfire, then you know what I’m talking about. Granted, that would be difficult to hear in real life as well, but the audio equipment involved in the process makes it pretty unintelligible. That’s where a compressor comes in.
我们正在谈论压缩音频轨道中声音的动态范围。 如果在TNT爆炸后录制图钉下降，您会注意到这两种声音的强度差异很大。 这就是我们所说的动态范围。 现在，我们的耳朵非常擅长处理类似这样的大差异，但音频设备却没有。 如果您曾经看过一部战争电影，演员的对话被枪声淹没，那么您知道我在说什么。 诚然，在现实生活中也很难听到这种声音，但是过程中涉及的音频设备使其很难理解。 那就是压缩机的来历。
The image above shows a rack-mounted compressor, which will take an audio signal and adjust it based on several parameters. It’s a lot like having a personal audio engineer that will constantly adjust the signal to where it “should” be, as it’s running through the system. Compressors are usually physical devices that process signals that can be chained to other effects and processors, but the effect can also be applied via software. You can adjust the levels he starts to turn the knobs at, how quickly he acts, and how much compression is applied over what time period, but that’s what his focus is limited to. This reduces the dynamic range in predetermined ways so that the result is uniform audio, or at least audio whose loud and soft ends are much closer to each other.
上图显示了机架式压缩机，它将获取音频信号并根据几个参数对其进行调整。 这就像让个人音频工程师在系统中运行时，会不断将信号调整到“应”在的位置。 压缩器通常是处理可以链接到其他效果和处理器的信号的物理设备，但是效果也可以通过软件来应用。 您可以调整他开始旋转旋钮的水平，他动作的速度以及在该时间段内施加的压缩量，但这就是他的重点所在。 这以预定的方式减小了动态范围，因此结果是均匀的音频，或者至少是响声和柔和的末端彼此更加接近的音频。
作为效果 (As an Effect)
Compressors can be used for artistic effect, too. It can enable singers to whisper just as loud as the distorted guitar. This result that wouldn’t really work as well by just adjusting the volume, especially if the singer suddenly switched from whisper to all out scream. Let’s take a look at some examples.
压缩机也可以用于艺术效果。 它可以使歌手像失真的吉他一样大声窃窃私语。 仅通过调节音量，这种效果实际上并不能很好地发挥作用，尤其是当歌手突然从耳语变为尖叫时。 让我们看一些例子。
For the Killers’ benefit, I’ll assume the effect here is intentional. You can hear when the bass drum kicks starting around 43 seconds in that the volume of everything else drops a bit. This particular use is often heard in the various techno-subgenres to accent beats. Though its use can be deliberate, this “pumping” is most often a sign of a badly- or over-compressed song
为了杀手的利益，我认为这里是故意的。 您会听到低音鼓开始鸣叫的时间约为43秒，其他所有东西的音量都下降了一点。 在各种技术子流派中经常会听到这种重音，以重音节拍。 尽管可以有意使用它，但这种“抽气”通常是歌曲压缩不良或过度压缩的信号
At 22 seconds in, you can hear Amy Lee push a high-powered vocal that’s close to a scream, but it sounds muted. At 1:29, you can hear the layered background vocals being whispered, but the volume is normal. And, of course, you can hear that pumping effect while the audience is clapping throughout the video.
在22秒的时间里，您可以听到艾米·李(Amy Lee)推高声音的声音，接近尖叫声，但听起来却无声。 在1:29时，您可以听到分层的背景人声在窃窃私语，但音量正常。 而且，当然，当观众在整个视频中鼓掌时，您会听到那种刺激效果。
Both of these examples show what DRC can do in isolated circumstances, i.e. as an effect on a particular clip. It’s somewhat harder to illustrate how compression is utilized in its more mainstream usage.
这两个示例都说明了DRC在孤立的情况下(即对特定剪辑的影响)可以做什么。 在更主流的用法中，很难说明如何利用压缩。
恒定体积 (Constant Volume)
Image illustrating various compressor configurations to limit volume (from Wikimedia Commons)
该图说明了限制音量的各种压缩器配置(来自Wikimedia Commons )
DRC works well as a more advanced volume limiter that prevents the signal from clipping, which can distort the sound quality and damage sensitive equipment. It’s universally used to smooth out an audio track so that when an equalizer is applied afterwards, you reap more of the benefits. DRC is also used in movies so that in loud scenes, you can still hear the actors’ dialogue, or so that the dying whisper of a victim is still loud and clear after the gunshot that ended him. It can still preserve some of the dynamic effects, however. Let’s take the example of a band.
DRC可以作为一种更高级的音量限制器很好地发挥作用，它可以防止信号削波，这会扭曲声音质量并损坏敏感设备。 它通常用于平滑音轨，以便以后应用均衡器时，您可以获得更多好处。 电影中还使用了DRC，因此在嘈杂的场景中，您仍然可以听到演员的对话，或者在枪声将受害者杀死之后，受害者垂死的耳语仍然清晰而响亮。 但是，它仍然可以保留一些动态效果。 让我们以一个乐队为例。
The drums are a really dynamic and overall loud part of a band. If the drum track is uneven, it’s pretty noticeable. Say the drummer’s tired or makes some slight mistakes throughout the track. Some parts of the track will have louder bass kicks than others. Using a compressor will even that out so that the lighter kicks will be just as loud as the normal ones, and the harder kicks will be toned down a bit. Snares can also by toned down by dampening the initial strike, thus allowing the “crack” that follows to become more prominent.
鼓是乐队真正动感十足的组成部分。 如果鼓轨道不平坦，则非常明显。 说鼓手疲倦或在整个曲目中犯一些小错误。 曲目的某些部分会比其他部分具有更大的低音。 使用压气机可以消除这种情况，以便较轻的脚踢声与普通的脚踢声一样响，较硬的脚踢声将被调低一点。 军鼓也可以通过抑制最初的打击来降低，从而使随后的“裂纹”变得更加突出。
On a bass guitar, the higher notes will be louder and punchier than the lower ones. A compressor will keep the low tones loud and higher ones soft. On the other hand, when you use slaps to accent, you can keep them from spiking too high and being distracting, but still keep them sharper than the normal bass notes. You can also increase how long the note is sustained at a higher volume.
在低音吉他上，较高的音符将比较低的音符响亮且有力。 压缩器将使低音保持大声，高音保持柔和。 另一方面，当您使用拍打来重音时，可以防止它们尖刺得太高和分散注意力，但仍要使其比普通的低音音符更尖锐。 您还可以增加高音符持续多长时间。
Guitarists often can get carried away with their playing. Compressors can make sure that the lightly plucked or strummed notes stay light and the heavier ones stay loud. After a certain point, heavy strumming starts to distort the audio. Setting the compressor’s threshold – more on that later – to less than that will prevent entranced guitarists from messing up the track. You can also alter the sustain.
吉他手经常会因为演奏而感到迷恋。 压缩器可以确保轻弹或弹奏的音符保持轻盈，而较重的音符保持高音。 在某一点之后，大量的弹奏开始使音频失真。 将压缩器的阈值(以后再说)设置成小于该阈值，将防止入门的吉他手弄乱轨道。 您还可以更改延音。
In the same vein as the bass guitar, singers tend to sing louder at higher pitches and softer at lower pitches, depending on their range. You can keep the singer’s pitches even without requiring the singer to put more or less power behind them.
与低音吉他一样，歌手会根据音高的高低而大声歌唱，而在低音高时则柔和。 您甚至可以保持歌手的音调，而无需其施加更多或更少的力量。
In these ways, dynamic range compression can be used to smooth out smaller fluctuations in performance by artists. This allows a more uniform sound but still allows musicians to deliberately emphasize certain notes and cadences. It doesn’t get rid of the dynamic range of sounds completely, it just makes it so that the musician has to put more effort into it. All of this is especially important at live shows where performances are highly variable and much more sensitive to the performers’ stamina and frame of mind.
通过这些方式，动态范围压缩可用于消除艺术家较小的演奏波动。 这样可以使声音更均匀，但音乐家仍可以刻意强调某些音符和节奏。 它并不能完全消除声音的动态范围，而只是使它变得如此，以便音乐家必须付出更多的努力。 所有这些在现场表演中尤其重要，在现场表演中，表演变化很大，并且对表演者的耐力和心境更加敏感。
In this example, the Cancer Bats decided to compress the dynamic range over the whole song, not one particular track. Pay close attention to the end of the intro, at around 14 seconds in. The guitar is loud when it’s in focus, but as the rest of the instruments kick in, it drops down and mixes in. The overall volume of the song doesn’t change through the transition. You’ll hear a bit of pumping, too, but not as much as in the other songs. Unless this is the specific effect you’re going for, this is often considered a “poor” use of compression.
在此示例中，巨蟹棒决定压缩整首歌曲(而不是某一首曲目)的动态范围。 请密切注意简介的结尾(大约14秒钟)。吉他对准焦点时会很大声，但随着其他乐器的弹起，它会落下并混入。歌曲的整体音量不会在过渡过程中没有变化。 您也会听到一些抽气，但是不像其他歌曲那样多。 除非这是您想要的特定效果，否则通常将其视为压缩的“不良”使用。
Here, Daath used DRC over individual instrument tracks. You can tell because the guitar in the first few seconds of the song is a particular volume, and it’s maintained through the rest of the song. Unlike the Cancer Bats’ song above, Daath’s song gets louder when the other instruments come in by a more noticeable amount. This is good example of “good” compression; as the Futurama quote goes, “When you do things right, people won’t be sure you’ve done anything at all.”
在这里，Daath在各个乐器轨道上使用了DRC。 您可以说出来，因为歌曲前几秒钟的吉他是特定的音量，并且在歌曲的其余部分一直保持着。 与上面的《蝙蝠巨蟹》的歌曲不同，当其他乐器的声调更高时，达斯的歌曲会响亮。 这是“良好”压缩的一个很好的例子。 正如Futurama的话所说：“当您做正确的事时，人们根本不会确定您已做任何事情。”
Ultimately, it depends on what you want. Professionals say that compression should be used on each individual track, then if needed, over the final track as a whole. Dynamic range is good because it adds flair, nuance, and color to audio. Compression is used to illustrate that where musicians want it to be, and that’s done by reducing variation elsewhere. On the other hand, compression can add its own effect to audio. Several artists and even the majority of some genres use this for a specific feel, as an artistic effect.
最终，这取决于您想要什么。 专业人员说，应该在每个单独的轨道上使用压缩，然后在需要时在整个最终轨道上使用压缩。 动态范围很好，因为它为音频增加了风格，细微差别和色彩。 压缩用于说明音乐家想要的位置，并且可以通过减少其他地方的变化来完成。 另一方面，压缩可以将其自身的效果添加到音频中。 几位艺术家，甚至大多数类型的艺术家，都将这种效果作为一种艺术效果来使用，以获得一种特殊的感觉。
压缩参数 (Compression Parameters)
Compressors are built in different ways. Some use tubes, others use valves, some use light sensors and LEDs, and the cheaper ones use solid state parts. Different types of DRCs will “color” the sound differently, albeit slightly. The goal isn’t to change the sound itself, of course, but having an expensive tube compressor that makes the audio sound warmer certainly won’t hurt. Whether cheap or expensive and regardless of the mechanism, they all work to see the signal and adjust the volume. Compressor effects essentially mimic hardware compressors; above you can see the pane for the compressor effect in Audacity. Both focus on a handful of parameters.
压缩机以不同的方式构建。 一些使用管，其他使用阀，一些使用光传感器和LED，而较便宜的则使用固态部件。 不同类型的DRC将对声音进行“着色”，尽管略有不同。 目标当然不是改变声音本身，但是拥有昂贵的电子管压缩器可以使音频变暖，当然不会受到伤害。 无论价格便宜还是昂贵，并且无论其机制如何，它们都可以看到信号并调节音量。 压缩器效果基本上类似于硬件压缩器； 在上方，您可以在Audacity中看到压缩效果的窗格。 两者都集中于少数几个参数。
Threshold: This is the level at which the compressor will act. This can be set to the minimum or maximum volume, but it’s more commonly used as a guide post at which the compressor enacts changes. After this point, increases (or decreases, if used to bump upwards) in volume are significantly dampened.
阈值：这是压缩机将起作用的级别。 可以将其设置为最小或最大体积，但更通常用作压缩机执行更改的指南。 此后，音量的增大(或减小，如果用于向上碰撞)将被显着抑制。
Ratio: This is ratio by which the exceeding output is reduced. A 20:1 ratio will reduce whatever exceeds the threshold by that much, so 20db over the threshold will come out of the compressor as 1db over. Because the decibel system is logarithmic, this is has a much more pronounced effect on the volume. Really high ratios, like 20:1, 60:1, or infinity:1, effectively hard limit the volume.
比率：这是超出的输出减少的比率。 20：1的比率将使超出阈值的任何内容减少那么多，因此超出阈值的20db将作为1db以上的值从压缩器中出来。 由于分贝系统是对数的，因此对音量的影响要大得多。 很高的比例(例如20：1、60：1或无穷大：1)有效地限制了音量。
Attack: The signal isn’t altered by the compressor immediately; there’s a slight delay. Attack allows you to control this delay. It’s measured usually in milliseconds, so higher values will allow spikes of volume through the threshold before behind compressed, making guitars sound more punchy. Lower values will help with hard limiting.
攻击：压缩器不会立即更改信号； 有一点延迟。 攻击使您可以控制此延迟。 它通常以毫秒为单位进行测量，因此更高的值将使音量峰值在压缩之前达到阈值，使吉他听起来更震撼。 较低的值将有助于硬限制。
Image diagramming a compressed signal in comparison to its original signal (from Wikimedia Commons)
与原始信号相比，压缩信号的图像示意图(来自Wikimedia Commons )
Release: Compressed sound can be immediately returned to their actual volume or they can held at the threshold for longer. Using a higher value for release will help increase the “sustain” of a guitar or bass, allowing for notes to be held out much longer.
释放：压缩的声音可以立即恢复到其实际音量，或者可以在阈值处保持更长的时间。 使用较高的释放值将有助于增加吉他或贝斯的“延音”，使音符的保留时间更长。
Knee: The Attack dictates how quickly the compressor will act on a signal that exceeds the threshold. Knee dictates how quickly the compression is applied to that signal. A “hard” knee means that as soon as the compressor acts, it fully compresses the signal. This works well when using the compressor as a volume limiter. A “soft” knee will gradually build to using full compression. This keeps vocals sounding natural despite using compression.
膝盖： “攻击”指示压缩器对超出阈值的信号采取行动的速度。 膝盖决定将压缩施加到该信号的速度。 “硬”膝盖意味着压缩器一作用，就会完全压缩信号。 当使用压缩机作为音量限制器时，此方法效果很好。 使用完全压缩后，会逐渐形成“软”膝盖。 即使使用压缩，这也可以使人声听起来自然。
Output: This is the output level, which can be modified. After compressing a track or signal, it can be brought back up to its full volume or cut to a lower one.
输出：这是输出电平，可以修改。 压缩轨道或信号后，可以将其恢复到完整音量或切成较小的音量。
Different instruments sound more “natural” with specific settings, of course. Do some research online and use your ear to experiment until you find the sound you want. You have to ask yourself “What does my track need?” Now that you know how dynamic range compression works, you can tinker with the sound for yourself.
当然，在特定的设置下，不同的乐器听起来更“自然”。 在线进行一些研究，然后用耳朵进行实验，直到找到所需的声音。 您必须问自己“我的赛道需要什么？” 现在您知道了动态范围压缩的工作原理，可以自己调整声音。
If you’re looking for more info, there’s a great post on the Seven Strings guitar forum on DRC.
如果您想了解更多信息，请在DRC上的“七弦”吉他论坛上发表精彩文章 。
翻译自: https://www.howtogeek.com/57903/htg-explains-how-does-dynamic-range-compression-work/