Not sure what all this loudness stuff is about and how it affects you? Confused about the difference between LKFS and LUFS? In part four of a six-part series, loudness expert Mike Thornton continues to answer these questions and many more in his premium tutorial series, which is now available for free.

What Has Gone Before

In Part 1, Why Do We Need Loudness? We clarified what we mean by loudness, investigated how our hearing works, why we have changed our audio metering systems and presented the solution to loudness changes that consumers complain about.

In part 2, The Development Of One Loudness Standard, we covered the development of one loudness standard. We explored how we arrived at a loudness measurement algorithm that works just like our ears and the various criteria we use to define and guide us when working to the new loudness delivery specifications, including K Weighting, the differences between Momentary, Short-term and Integrated loudness as well as the importance of True Peak and Loudness Range.

In Part 3, Calibrating Your Monitors, we covered a key part of delivering loudness-compliant content - how to calibrate your monitors.  We looked at how our monitoring should be configured and provided an explanation of bass management and what your sub should be doing before moving on to a practical demonstration of how to calibrate your monitoring with a sound pressure meter.

In this free tutorial, we are going to share some tips and tricks for mixing to the loudness standards, which will include examples and demonstrations and explain the importance of what Mike describes as ‘loudness planning’ before ending with some specific tips and tricks for mixing short form content like adverts and promos.

Mike goes on to look at the changes needed to mix content for Netflix with the need to mix to a spec built around a dialog-gated algorithm and a target loudness of -27LKFS.

How To Create Loudness-Compliant Mixes For Broadcast

Before the move to loudness-compliant deliverables, I had to mix programs so they would survive the transmission processing rather than create the mix I wanted.

Once again, we can trust our ears because when we set the monitoring level to the appropriate level and start mixing, the amazing thing is that our mixes come out right and, with a little practice, will hit the appropriate target loudness. Because our hearing is very good at perceiving loudness by setting the monitor levels appropriately, it just works. But hitting the target by ear is much harder if your monitoring isn’t calibrated. For example, I was mixing a program quite early in the morning, and so as not to disturb the family, I had my monitoring lower than normal. I missed the loudness target and had to adjust it in post-production.

People often ask how they will know how to get mixes to hit the target. There is an interesting fact that not a lot of people know, and that is if you set your speech level as before so that it peaks around -10dBFS or PPM 6 here in the UK, then measure it with a BS1770 loudness meter, it will come out at around 0 LU - the target loudness. Obviously, compressed speech will be perceived as louder, so it will also read slightly higher, but uncompressed speech at a normal level will come out at target loudness. In fact, one of the ATSC A/85 test files is a sample clip of speech that hits the ATSC target loudness of -24LKFS.

Peak Reading Meters - Stay Or Go?

As we moved from peak metering to loudness metering, people asked about whether to remove the old peak reading meters. For me, it is a matter of personal preference; although some people are adamant that all peak reading meters should be removed, some folk prefer to retain them as a known reference point. Ultimately, it’s up to you. I had a BBC PPM in my studio, but I found myself looking at it less and less, so in the last upgrade, I chose to take it out,

Mix to -3dBTP To Be Ready For Lossy Codecs

Then, when it comes to peak level, consider only going to -3dBTP because lossy codecs used to deliver content digitally, like mp2 or mp4, will distort if the input audio goes much above -3dBTP. With peak normalization and having a ceiling at around -10dBfs it wasn’t an issue because we weren’t close to digital headroom, but now because we can go up to -1dBTP with the EBU R128 spec or -2dBTP for the ATSC A/85 spec if we don’t do something about it when it gets to the coding stage in the transmission chain, the peak levels will need to be restricted to -3dBTP to meet the transmission specs to protect the lossy codecs, so why not create content that only goes up to -3dBTP so that the audio doesn’t get modified before it goes through the lossy codecs.

Hardware Loudness Meters For Live Mixing

For areas handling live audio, like studio control rooms and transmission areas, the TouchMonitor loudness meter is becoming very popular. You also might like to consider including the TC Electronic loudness radar option for your hardware loudness meter. The radar histogram is very helpful in giving a sense of where the loudness trends in your mix are going, especially as the nature of the radar display effectively means the histogram folds back on itself.

Use the meter in relative mode so that the target loudness is 0LU. It is easier to aim for, and if you are high or low, it is clearer as it will be displayed in negative numbers below and positive numbers above the target loudness.

Colour Choice Tips For Hardware And Software Loudness Meters

Do experiment with the display preferences, especially the colours for different loudness to help you get a sense of loudness with just a quick glance at the loudness meter.

A number of sound mixers have settled on a colour scheme, as shown in the diagram above on the left-hand side. Using green bands for each of the three loudness meters makes it easier to hit the target loudness. A popular configuration is having different green zones for each meter.

On the momentary meter, which is averaging the loudness over 400ms, have a green zone 3 LU above and below your target. With the short-term meter, which averages over the last 3 seconds, set the green zone to plus & minus 2LU, and the Integrated loudness, the average for the whole program, set your green zone to just 1LU above and below your target loudness.

Then use red above your green zones and blue below, all of which will make it very easy to see how close you are to the target. Remember that the momentary loudness will vary the most so significant swings in momentary loudness are absolutely fine. The short term will vary but somewhat less that the momentary meter and the Integrated will stabilize very quickly and only move quite slowly.

Where it isn’t possible to change the colour zones for each meter, I have configured my VisLM plugin to have a green zone for +2LU to -3LU.

Always Use A True Peak Limiter

In live situations, you should always have a true peak limiter in your studio output. Most digital limiters are sample peak limiters and so will allow intersample peaks through unlimited. Because true peaks can be anything up to 6dB higher than sample peaks, and we are now working within 3dB of digital headroom, it is essential that your output limiter is a true peak limiter and not a sample peak limiter. 

There aren’t that many hardware true peak limiters out there, and if yours doesn’t shout it from the rooftops, then it almost certainly won’t be a true peak limiter. For a long time, there was one main contender, and that was the TC Electronic DB6, but more recently, the TC Electronic LM2 has been finding favour as a more cost-effective solution.

So that we can be confident that the mix we create is the same mix the consumer enjoys the true peak limiters should be the only processors in the delivery chain, all other dynamics processors should be taken out otherwise we end up fighting the transmission processing all our again.

Remember to set your true peak limiter to -3dBTP so as not to overload the lossy codecs.

Loudness Planning

Whether you are mixing live, or working in post-production, loudness planning should become an integral part of your workflow just as planning for channel and track counts, desk layouts etc, are all essential parts of good preparation, so loudness planning should become a critical part of the process whether you are working in a live or post-production context. 

As you plan your mix, consider the comfort zone. The comfort zone has come out of all the listening tests that have gone into the development of the loudness standards. What they found is that there is a zone within which consumers don’t feel they need to reach the remote control to adjust the volume. This comfort zone is between +3LU and -5LU around the target loudness and is a useful guide to consider for the short-term meter.  If the loudness goes outside this comfort zone for a significant period of time, then consumers will reach for the remote control, which defeats the object of the loudness workflow.

We recommend when mixing for post-production to do their dialog mix pass first the the aim of getting the dialog to stay fairly close to the target loudness. Then, on subsequent passes, add and mix the music and effects, setting them around the foreground sounds (usually the dialog) as feels appropriate. If you have calibrated monitoring then if an element feels loud then it will be loud, if it comes across quite it will be quiet, you can trust your ears.

Because it is harder to bring the average down, especially on the louder shows, consider running the opening credits and any other packages that will be played throughout a show, slightly lower. Because they are pre-recorded, consider running them through a loudness meter before the show and then playing them in a little quieter. Because these packages will now be a known loudness, this will also also help you keep track of the loudness and you will find it easier to mix live shows very close to target loudness. Established mixers can mix live shows to within 0.5LU using these techniques together with calibrated monitoring.

This is especially important on the louder types of shows like light entertainment with a live audience because it is very hard to bring the average down especially once you have passed the 10 minute mark. Check out the video for an example, which is the exception that proves the rule.

Consider Reducing The Attack Of Your Compressors

Because we can have a wider dynamic range and we are no longer constrained to a maximum peak level, we can now configure our compressors with a slower attack, which will allow the transients through but with manage and control content if it consistently stays loud. We can still use compressors and limiters to manage surprises, especially on live or as live shows but having more transients come through the mix will help to open up our mixes.

Mixing Tips For Adverts Trailers and Promos

When it comes to advert and promos often called short form content, all the rules still apply as well as all the opportunities for increased dynamic range and impact moments. However because of the intense loudness wars of '“I want my ad to be louder than anyone else’s” all signs of dynamic range have been squashed out of short form content. I am aware that clients have rejected mixes with just 4dB of dynamic range as being too much! They were only satisfied when the ad was remixed with no more than 2dB of dynamic range.

The loudness standards mean that there is no point in having content that is so heavily compressed to make it louder. If you do it will simply be turned down until it meets the target loudness.

However, people started looking for other ways of creating adverts that had an impact but met the spec. One trick was to create an ad where the first 25 seconds or so was very quiet and then drop in a really loud payoff line that, when averaged over the whole ad, would hit the target loudness.

A Change To The Delivery Specs 

Consequently, in a number of territories, they have added a requirement for a maximum short-term or momentary loudness for any short-form content. For example, the PLOUD group responsible for the EBU R128 standard published a revision to R128 for short-form content, that is, anything less than 1 minute in duration, which specifies that the highest the short-term loudness can go is +5LU. Remember that normally, there are only two pass/ fail criteria: the integrated loudness and the maximum true peak. The momentary and short-term measurements were only there as a guide to help us mix loudness-compliant content. Now, a maximum short-term or momentary figure has been added to the pass/fail criteria for short-form content.

However, just as for long-form content, we can add more dynamic range so we can for short-form content, too. In the video, I play you two mixes of the same spoof ad, one mixed to a maximum peak level of -10dBFS and then the other to a target loudness and with more dynamic range; take a listen and watch the quasi-peak and loudness meters as well.

You can see from the histograms that the first version has very little dynamic range and is much louder than the second loudness-compliant mix, which also has more dynamic range. In the second mix, the second half of the mix is quieter and more restful, which sits better with the story. In addition, the explosions cut through the mix and have much more impact than they do in the first mix because they simply bash into the peak limiter.

As we get more experience and these concepts are introduced into the creative brief, we are seeing more opportunities for more dynamics in ads and promos. Take a look at the histogram for two different mixes of a Pet Rescue ad.  The ad opens in a museum before the music and effects kick in halfway through. However, in the peak normalised mix, the museum sounds are as loud as the music and effects, whereas, in the loudness-compliant mix, the museum section is much quieter, as you would expect, and then when the music and effects kick in, they have much more impact.

In Conclusion

To recap, the opportunity to go through the roof beyond the old -10dBFS ceiling is very liberating and enables us to have those moments of impact where we can make things louder if we want to as long as the overall loudness for the whole program averages out.

We can add dynamics to our mixes and get away from the uniformity that we used to end up with when normalising and working to a maximum peak level, often referred to as ‘the sausage mix’.

Working to these new loudness standards is liberating, we an set our monitor level and mix trusting our ears, knowing it will come out right and we will hit our target loudness.

What About Loudness Workflows For Netflix?

What we have talked about so far largely relates to audio post-production for broadcast content, whether that is delivered to the consumer by cable, terrestrial transmission or satellite transmission. But with more and more content being delivered by streaming services like Amazon or Netflix. Do we have to amend the workflows outlined above to meet the requirements of Over-The-Top (OTT) and by Online Video Distributors (OVD)?

The Audio Engineering Society (AES) published Preliminary Loudness Guidelines in September 2016 that aimed to address the fundamental concern of audio Loudness in the developing segment of on-line television and video content delivery, from creation through distribution and to the consumer experience.

Then in October 2017, the AES followed that up with the full Loudness Guidelines for OTT and OVD Content.

In 2018, Netflix published their Netflix Sound Mix Specifications and Best Practices, which brought back the use of Dolby’s Dialog Intelligence software that was used by some broadcasters in the 90s as part of the Dolby Digital AC3 workflow using Dolby’s Dialogue Intelligence, their speech-gating technology, which measures loudness only on the segments of a program that contain dialogue.

This workflow was built around using the dialog loudness as the anchor or reference point and normalising to that, to enable content creators to set dialogue to a fixed loudness and mix the other content around it, based on the idea that viewers typically adjust their television volume controls according to the audibility and intelligibility of dialogue.

This differs from the BS 1770 based workflows, which use the loudness of the full mix, rather than just the dialogue, to normalise the loudness for each piece of content.

Here in Europe, Dolby’s speech gating technology never really got a foothold in broadcasting, we went from peak level normalisation straight to BS1770 loudness normalisation working to EBU R128.

Whereas in the US and Canada, Dialnorm and Dolby’s Dialog Intelligence and the use of the Dolby Media Meter were in common use but slowly phased out as broadcasters moved over to full mix normalisation.

Rolling forward to 2018, the industry was shocked when Netflix published their delivery specs to find that…

“Average loudness must be -27 LKFS +/- 2 LU dialog-gated. Peaks must not exceed -2db True Peak. Audio should be measured over full program according to ITU-R BS.1770-1 guidelines.”

Because we hadn’t used dialog gating for so long and Dolby had discontinued their Dolby Media Meter in August 2018, the phrase dialog-gated caused a lot of confusion. The other point was the normalisation number was -27LKFS, rather than -23LUFS or -24LKFS. Again an echo back to the old Dialnorm number.

If you want to get the full story and find out what we thought of this move by Netflix then check out our very comprehensive article Has Netflix Turned The Clock Back 10 Years Or Is Their New Loudness Delivery Spec A Stroke Of Genius?

Following this article, Scott Kramer, Manager, Sound Technology | Creative Technologies & Infrastructure at Netflix reached out to us to respond to our article, and here are some excerpts from that response…

“In writing our specifications, we seek to preserve the best possible experience for Netflix members, while protecting the creative freedom of the creators. In the case of the new loudness specification, both groups were aligned. Many Re-Recording Mixers asked for dialog-based measurement to simplify their workflow and to ensure loudness consistency for the audience….

… With the new spec, we sought to change how mixers measure, but not how teams mix. We measured our content which was compliant for the -24 LKFS +/- 2 LU full program spec, and found that dialog levels clustered around -27 LKFS. This approach, by using the dialog loudness, allows for as little workflow change as possible, while providing more dynamic range for creators that feel they need it. The choice of stating a 1770-1 measurement comes from the Dolby Media Meter terminology for a dialog based loudness measurement. Dialog based loudness measurement does not require the use of the relative-level gate specified in BS.1770-4, as the DI algorithm already applies a gate (a dialog-based gate) to the audio.”

You can read the response in full in our article.

Netflix Loudness And Dynamic Range Developments Update

Netflix continues its work to improve the experience for its subscribers across a variety of devices. In this article, drawn, with permission, from a post on the Netflix Technology Blog, we explore how they measure program dynamic range and then use dialog normalisation and dynamic range reduction to improve the experience for subscribers, especially those using mobile devices.

In this article, we cover the following…

• Dialogue Levels and Dynamic Range

• Loudness Management

• Peak Audio Sample Metadata

• Putting it Together

• Seamless Switching and Adaptive Bit Rate

• Deployment, Testing and Observations

• Volume Level

• Volume Changes

• Audio Sink Changes

• Conclusions

• Acknowledgements

You can learn more in our article Netflix Loudness And Dynamic Range Developments Update.

How To Optimise An Audio Mix For Delivery To Netflix

To help the growing number of audio professionals creating content for Netflix, the streaming company has produced a tutorial video designed to provide useful advice on how to optimise a mix for their streaming audiences, insights on how Netflix members consume Netflix content, as well as sound mixing guidelines and deliverable requirements for original version sound mixes, M&E mixes and alternate language sound mixes.

In this video, Netflix talks about sound mixing for Netflix, aiming to answer these questions…

• How should I prepare sound mixes for Netflix?

• How should I prepare M & E mixes for Netflix?

• How should I prepare dub mixes for Netflix?

• What is the purpose of Netflix sound specifications?

• How may I ensure a sound mix plays well on the service?

• How does Netflix process and stream sound mixes?

• How does Netflix optimize sound experiences for members at home?

The goal is to enable a clean sound pipeline from the microphone onset to the speaker in a Netflix member's home by protecting the sound pipeline, we're able to provide members with the sound mix that the creator's intent.

If you would like to also read a full transcript of this video with stills from the video then check out our article How To Optimise An Audio Mix For Delivery To Netflix.

What Next?

In part 5, Preparing Content For Music Streaming Services, we will cover loudness online content and music streaming services, including the various standards for online content, loudness normalisation, album normalisation, and how to prepare music tracks for music streaming services with three free video tutorials.

In part 6, Using Loudness Meters For Music And Post Production, we will end the series by listing our selection of loudness meters in alphabetical order, and as we mentioned at the start, please note that this isn’t an exhaustive list. Where we have them, we will include tutorials and reviews of each of the meters.

Why Is It Now Available For Free?

This series, originally released in 2016, was on our premium tutorial channel. Since the platform on which it was hosted closed down, this much-loved resource has not been available. Rather than find another platform, Mike has decided to make the entire course available completely free. We will be releasing the complete series over the coming weeks, all of which you can access completely free.

In just over 1 hour, Mike Thornton helps you understand how the new loudness standards affect you and the clients you work for. Mike has been delivering loudness training courses to broadcasters in the UK, Europe and further afield, and with this tutorial series, you too can benefit from his expertise.

Who is this course for? 
Although it is aimed at people working in broadcast and OTT environments, they need to produce content to comply with the loudness delivery specifications like ATSC A/85 for the US and Canada and EBU R128 for Europe, including live audio mixers, audio post-production editors and mixers, compliance teams, as well as video editors, and others working in the delivery of broadcast content, the first three tutorials in the course will be very helpful for people working in music production, who need to deliver loudness compliant mixes to any service using loudness normalisation.

What does the course cover?
In this series, we start by answering the question, ‘Why do we need loudness?’ We go on to cover the difference between peak level normalisation and loudness normalisation. We look at the history of audio metering and how the loudness standard has been developed and learn that the different delivery specifications around the world are, in fact, all based on that one standard. We show how to calibrate your monitor speakers, which is an essential part of mixing to loudness, before moving on to some tips and tricks on how to mix to comply with the new loudness standard and delivery specifications. 

How Much Does This Tutorial Series Cost?
This course was available for rent on our premium tutorial channel and cost $49.99 for one year. It is now available completely free at no cost.