如何掌握混合事件的数字音频混合艺术
为场地混合音频是一个有充分记录的实践. 在最基本的层面上, 它需要麦克风, 预先录制的音频源, 一个音板, 喇叭, 和, 最重要的是, 熟练的操作员. The two most common challenges with live-venue audio are avoiding 和 eliminating feedback 和 ground-loop hum.
Mixing audio for a video recording or live stream involves many of the same techniques 和 equipment, but each has different production st和ards 和 you don’t have to worry with live sound reinforcement using 喇叭. The two most common challenges with audio for a live stream are attaining a clean signal 和 mixing audio within a smaller range than you might if you’re only mixing for the venue.
这两者的解释和实现都不是很复杂, 虽然, 在实践中, 由于房间动态的原因，混合现场音频非常具有挑战性, 电气接地问题, 和, 最重要的是, 麦克风技术.
作为直播专家, my perspective is going to be different compared to how a live audio technician would approach venue audio. The main reason is that I’m considering both the in-person audience 和 the live-stream audience equally 和 simultaneously.
在本文中, I explain my approach to mixing audio for both of these environments at the same time. 在我的事业中, I refer to events that have both an in-person audience 和 a live online audience as a hybrid event, 我们制作的大部分作品都是针对双重观众的混合活动. 随着时间的推移, 我们发现我们更喜欢为两种用户处理音频, 而不是将其部分或全部委托给外部影音公司. The biggest reason is that the needs of the audience in the room are different from the needs of an online viewing audience, 和 if an audio technician is mixing audio only for the room 和 is not involved in or monitoring the audio for the live stream, 音频级别可能不在理想的范围内.
So, 把那篇冗长的序言去掉, 让我们从现场混音的基础开始.
步骤1:连接音频源
Connecting microphones 和 预先录制的音频源 to 一个音板 is best done with balanced connections like XLR or ¼" TRS cables. The use of balanced connections helps reduce external noise from electromagnetic interference, 对于更长的电缆线路来说，这是一个特别的问题.
步骤2:设置前置放大器电平
当你把电缆连接到音板上时, 不管它是数字板还是模拟板, 您需要为每个输入设置前置放大器电平. 前置放大器水平也可以标记为增益或修剪. Some boards have a levels indicator that is green when you’re in the correct range 和 red if your signal is too hot. With all audio signals, you never want to clip your audio anywhere in your signal flow. 这类似于拍摄视频时保护你的亮点.
步骤3:确认干净的音频
您可以用耳机或扬声器确认干净的音频. This is when you listen for obvious problems like a ground loop hum or a noisy or distorted audio signal. 当你将A/ c供电的音频设备连接在一起时，会发生地环路嗡嗡声. 正常情况下, 设备接地到它直接连接的空调插头, 但有时, 由于接地电位的差异, 设备通过音频电缆选择阻力最小的路径, 不要把插头插到地上. 这会导致地环路嗡嗡声.
这种电子干扰嗡嗡声需要消除. 解决方案是添加一个直接盒(又名DI)， 下面的图1)进入工作流程，以提升地面并迫使设备接地, 按预期, 连接到各自的插头上. Using a DI should be done automatically when you are connecting audio from a remote laptop both to lift the ground 和 to convert the unbalanced signal to a balanced XLR connection.
图1. A 百灵达迪
步骤4:设置PA扬声器和音板音量级别
I start with my PA speakers set to one-quarter volume 和 then I increase the volume levels for each input 和 the main output. 如果你的水平设置得当, you should be operating in a range where the levels for the inputs 和 output are just below the parity level of 0 on the level faders. 如果你的音量调得太高, 那么你就没有能力在需要时提高等级, 如果它们必须设置得太低, this means that your 喇叭 are set too high 和 the signal for the live stream won’t be within a desirable range.
It might take a bit of back-和-forth to find the right balance between the levels on your 喇叭, 输入量, 主要输出量, 但这都是混合专业音频的一部分. 在这一步中, you are generally getting the audio into a proper range so that you can move on to the next step; you can then return to this step to get your final show levels set.
步骤5:平衡音频
一般, 这一步是第四步的一部分，因为, 大多数时候, 在设置音频级别时，你会发现这一点, 你可以在音频呈现关卡前获得反馈. This is especially relevant when you have multiple microphones 和 especially with omnidirectional microphones like lavaliere mics. Feedback is what happens when certain audio frequencies bounce around the room 和 back into the microphones at a higher level than the other frequencies. 这创造了一个反馈循环，立即变成了不断增加的尖叫. 必须通过手动降低水平来立即终止.
Every room is different in terms of which frequencies will bounce around more than others. 一些音频技术人员声称他们可以听到并识别反馈频率, but I prefer to rely on simple frequency spectrum analyzers to identify exactly which frequencies are ringing. 如果我用的是数字音板，比如贝林格X18 (下面的图2), I can consult the 100-b和 Real Time Analyzer (RTA) to monitor 和 identify the problem frequencies, 然后使用均衡器只在那些特定频率上调低电平. 这比降低整个频率范围更精确, 就像在大多数模拟板上一样, 这也是我更喜欢数字音板的原因之一.
图2. 贝林格X18 数字音板
Audio equalization (EQ) can be done on individual inputs or the main output as a whole. 正常情况下, you would add a bit more EQ on those previously mentioned omnidirectional microphones that are more prone to feedback 和 less on a cardioid h和held microphone. You also want to be careful not to go overboard with carving out too much when you are EQ’ing, 或者产生的信号听起来太像在鱼缸里录制的了.
On an analog soundboard, you’ll be more limited with how surgically precise you can get. 大多数板限制你只有三个控制:高，中，低. 我觉得这个限制太大了, 但这是大多数小场馆运营商使用的方法, 它强化了我管理自己音频的偏好.
我最喜欢的模拟混频器系列是麦基ProFX V2系列(下面的图3) because the eight- 和 12- channel models that I use have a seven-b和 stereo graphic equalizer, 这让我比传统的三通道均衡器更精确. Unfortunately, the new V3 line eliminated the graphic equalizer in favor of a compressor.
图3. 麦基ProFX V2 模拟混合机
之前我搬到一个数字混频器与100波段图形均衡器, 我使用了贝林格FBQ1502HD 15波段均衡器. Although it does feature feedback detection that lights up the frequencies that have the strongest signals, 我发现假阳性太多了, 我用外部频谱分析仪得到了更好的结果. 这可能听起来像是一项奇特的技术, 类似于昂贵的曝光测光表, 但我说的是免费的, 可下载的名为高级频谱分析仪PRO的手机应用程序(下面的图4)，也没有广告.
图4. 先进的 频谱分析仪 PRO安卓应用
EQ’ing a room is as simple as slowly increasing the volume on your soundboard until you start to hear feedback. 然后, 使用RTA或频谱分析仪, 你决定哪个频率是尖峰并引起反馈. 接下来在你的图形均衡器上，降低特定的频率. 然后，您可以再次增加音量以瞄准下一个最差的频率.
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