A couple of questions about Audio Gain
Hello everyone! I'm somewhere between a complete noob and Intermediate level user of Premiere Pro and absolutely love working with it. Also, long time lurker of this sub.
I went on a 2-day course in London recently to learn the software, and the bloke there mentioned something about Audio Gains and best practice for it that I thought I'd share here to try and understand the concept better.
He said that at point of importing audio tracks into a timeline or before exporting a final video, one should always check to see whether the audio peaks are getting exceeded past danger levels (the red zone).
If they are even once, the instructions were to right-click the audio track (or all of them together), Select Audio Gain, and normalise all peaks to -8db.
Unfortunately I didnt have time to get into asking what exactly was going on here as the class was wrapping up. So here's a couple of questions:
A) Is this process something one needs to do for all scenarios with audio tracks, or is it a case-by-case basis?
B) What exactly is going on here? I'm clearly not lowering the volume of the track, because I can always raise it in the sequence, right? What's making those peaks smaller and why -8db specifically?
Any help with this would really help. I'm trying to understand what I do as I go along editing and improving my skills. I'm not an editor by profession, I just make some small 1-2 minute videos for the company I work for! I'm really enjoying this work and am looking to improve skills further and see if this is a possible career switch for me in the future.
Thanks!
Posted Feb 29, 2020, 4:38 PM UTC
Final delivery and whatnot are going to matter. You don’t mix levels for a Star Wars movie being shown in a theater the same way you mix a news report for TV or the same way you mix an unboxing video that’s is going on youtube. So, no, simply setting your peaks to never go above -8dB is not some universal truth, far from it. Honestly for youtube you have to imagine people are watching on shitty laptops and phone speakers, and under those conditions they “need all the help they can get” so to speak, so having your peaks at -1dB is not uncommon, if anything it’s damn near required, those tiny ass speakers even at full volume the device can go, won’t be all that loud. If your content is several dBs lower than everyone else’s then it’ll stick out in a bad way
But if you’re making a commercial going out for TV, almost every country or region has actual laws on the books about how “loud” a mix can be, and the tool used to measure that is more involved than simply peaks....due to human perception, a momentary peak that’s 7 dB louder than the 10 seconds before or after it doesn’t sound loud, but sustained higher peaks over time will....so it’s literally a tool that reads the loudness and makes a real time measurements...you essentially have to let the tool run over the entire video and see if the readings meet the specs laid out for for your country. The USA and European loudness for TV are very similar but just ever so slightly different. -23LUFS and -24LKFS with additional rules about no X minute section can be +/- a couple of dBs...so a 60 minute broadcast as a whole needs to be the -23 spec but you can’t like have 5 minutes super loud and 55 minutes way too low, even if the overall reading fits, you can’t waiver too much, it still needs consistency.
Also, note not the same thing as saying your peaks don’t go over -23 or -24dB on your premiere or whatever digital audio meters. In fact that would be far too low. I bet the -8dB the guy told you is a decent reference number for UK TV broadcasts for dialog. But it’s all about dynamic range and overall mix. You don’t want your speaking parts and your, say, explosion sound effects to be wildly different, Tv speakers are better than laptop but not much, so that’s a consideration in your mix. I don’t deliver for TV myself, but I’ve messed with the tools that read loudness for the various laws, and I find that my dialog speaking between -10 to -6dB will read out pretty damn close to the -23 LUFS loudness over time spec.
Movie theaters tend to have far greater dynamic range in their mixes than TV does, and yes, when a movie gets put on DVD or Blu-Ray, they do a new audio mix that has a different dynamic range than the theatre mix.
Just as a note: a dB (decibel) is a meaningless number without a scale. Like with temperature degrees. If I say it’s 10 degrees outside, it makes a HUGE difference if I mean 10 degrees Celsius or 10 degrees Fahrenheit or 10 degrees kelvin. A degree number by itself needs the right scale...same with audio dB numbers. The digital scale Premiere uses is just one such scale.
Thanks for the detailed response. You lost me a little bit with the end of your second paragraph though, perhaps because I don't quite understand audio the way you do! Particularly that last sentence.
But if I could venture a learning from what you've said overall, I'd imagine it's something like this. Do correct me if I've got some part of it wrong.
There are specific laws (based on locvation, UK/US/Europe governing what audio levels you need to aim for, based on the output of what you're editing, i.e. whether you're editing a YouTube video, TV broadcast piece or cinematic film. Follow up question: is there a place where this is documented that I can know and follow up on for future edits?
Peak adjustment is a way to balance overall sound of different audio tracks to get to an equilibrium that's both comfortable for the listener and hits said country standards as defined in Point 1.
Have I got that right?
The laws ONLY are for traditional broadcast TV. YouTube is the Wild West bro, anything goes. Netflix I don’t think has to follow any laws but they have their own specs and will reject things that don’t meet it, how much it matches any laws I’m not sure. But the laws are just for TV stations. Internet, no laws brother.
Peak adjustment isn’t the end all be all...there is also compression. How the audio was recorded and how it is when it’s been edited and mixed will almost always have been compressed, in that the dynamic range will not be as wide. For example during an,interview, someone is talking and then all of the sudden they laugh. That laugh will be much louder and recorded much louder than their speaking voice. But you don’t want this for your final mix. You want the laughing and the normal speaking to not be nearly as much difference in levels, if hardly any at all.
Just making peaks have a threshold of -8dB (or whatever number) may make the laugh lower, it it doesn’t make the normal speaking parts louder. In fact I forget exactly how the “set peaks to XdB” works in premiere but it might make EVERYTHING in that clip lower in the same way...if the laugh’s peak is lowered by 3dB to get it down to -8, then the dialog will be lowered by 3dB also. Setting peaks is different than a limiter which cuts off the wave at a number but doesn’t lower the entire clip. A compressor can act like a limiter, but a limiter isn’t a compressor.
I was just about to recommend compression instead of brick wall limiting. Just lowering the overall gain so the peaks are -8 is not what you want to do most of the time.