Sound Mixing for Film, Loudness

So when we're doing sound mixing for film, we really need to pay close attention to loudness and loudness metering. There are common specifications that are pervasive in the industry and we really need to be following those if we want our mixes to come out at the right level and not be rejected in QC. So first of all, what is loudness or loudness metering? They came up with this, I don't know, about 10 years ago because we were using VU metering or what we call peak metering and engineers figured out that if they applied a lot of compression and limiting and basically smashed the mix as we call it, so really compressed and limited down all the louder stuff, they could then basically hit the same VU peak number as someone else but their content was a lot louder. So they finally decided, meaning the, you know, the distributors and probably working with the SMPTE, the Society of Motion Picture and Television Engineers, that they needed a better system, some way that they could really base how loud something is, not just by looking at the peak volume, which is what we did before. So they came up with loudness metering and there are two things that show up as settings on the meter that you might be already a little bit familiar with, but you either use LUFS or LKFS. Now you can research the difference, I actually have pretty recently, and the gist of it is there is no difference. LUFS and LKFS, I think initially there was a slight difference but nowadays the way they've refined them, they do basically exactly the same thing. We tend to see LUFS a bit more in the delivery specifications, but honestly if you were set to LKFS as opposed to LUFS, it would really make no difference. Let me show you what I mean on the computer. Okay, so here is the WLM loudness meter. This just happens to be the one that I like, this one is made by Waves. The other one that a lot of people use is iZotope Insight, also very good. I mean, really the meter just has to show you that it can read loudness, so whichever one you can get your hands on. There is actually a loudness meter in, I believe it's the Pro Tools Pro Limiter that comes with certain versions of Pro Tools, so you should check out Pro Limiter, see if the LUFS and LKFS metering is available in there. So the main thing is for the entire program, we need to hit a number of minus 24 plus or minus 2 if it's for TV distribution or TV streaming. If we're doing a film project, we need this number long term to be minus 27 plus or minus 2. So as long as you're in the range, you're good, you're So let me just play a little dialogue here and let's see what the meter is saying. Now I'm not feeding audio because I just want to demonstrate what the meter does. So you can see my short term is showing minus 27 and my long term is just reading minus 26. So this dialogue can come up if I want to adjust the volume up and it's not so important what the short term is, right? This can it can be minus 20, which is louder, or it can be minus 27 minus 28, as long as in the end, the program comes out to be minus 24 plus or minus 2 if it's, you know, TV or streaming or minus 27 if it's for theatrical. So that's the main thing you need to know. The other thing that's very important, though, is for loudness specification, we usually have to hit a DB true peak DBTP. So that is, you know, the true peak loudness limit that's allowed. In general, we find that a DBTP DB true peak of minus two is the most common specification that we see. You might, if you're doing film, be able to get away with a higher limit. But if you want to just play it safe, running this at minus two, in this case, you know, there's a limiter here that actually allows me to set the true peak max at minus two, or you can set another limiter to keep this at minus two, but you can't go over that in most cases. All right, that's a pretty simple explanation of what the meter does and how it reads loudness. Again, the long term is what's important, and that you're not exceeding whatever DB true peak is specified. But in most cases, that's going to be minus two. Okay, that's basically the skinny on loudness and loudness metering. But you have to ask for and check specific audio delivery specifications for any project that you're doing. You have to be following exactly what they want you to do. I hope you found this helpful. As always, like, comment and subscribe. See on the next one.