Loudness management

Stricter regulations for audio loudness levels require ubiquitous standards and future-proof technology.
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Mixer Andy Hagon uses DK-Technologies’ MSD600M++ audio meter in a sound suite at Pinewood Studios, UK.

For years, audio professionals in the production and broadcast industries have been attempting to control audio so their audiences aren't irritated by surprise level changes in both commercials and program material.

Although this has recently become a key issue, it has actually been a problem for a long time. The industry used to deal with it by relying on skilled technicians who would sit behind the console and protect the transmitter by making sure peak levels were not exceeded. They would also protect the audience experience by ensuring that the loudness of program material and commercials remained reasonably constant. However, the introduction of automation changed all that. Now, with output automatically controlled, it is much easier for advertisers to manipulate audio so their commercials seem louder and are more likely to grab the viewer's attention.

Loudness differences have led to many complaints from viewers, particularly from those who don't like the large swings in volume between programs and commercials. The complaints were so vociferous that it became increasingly clear that a solution was imperative.

When dealing with audio loudness, the first thing a broadcast engineer must do is measure the signal, because it is only through accurate measurement that he or she can decide if the signal is falling within defined parameters.

With so much emphasis now placed on loudness, audio metering manufacturers have responded by introducing new tools to identify and help solve the problem.

Metering

Historically, the evolution of audio metering has established both quasi-peak and average reading meters as tools regularly used by broadcasters and those making programs and adverts for broadcast. What now needs to be considered is whether those meters need to be replaced or supplemented by newer designs that take into account additional parameters, including program spectral content and amplitude.

Because audio is an electrical signal with a limited bandwidth, it is possible to measure the voltage by using measurement instruments. These instruments use logarithmic scaling and can have different characteristics and level-meter display ballistics. A standard audio level meter is not very precise when it comes to following the peaks of the audio voltage, but that is not really a problem because many peak transients don't transport much acoustical energy. In other words, they are mostly inaudible.

One might think that by combining measurement with monitoring (listening), it is possible to control the audio content. But as engineers the world over have discovered, two pieces of audio with the same audio level can actually sound very different. What's more, the loudness impression can also sound different. There are many reasons why this is the case, not least the impact that spectral composition, equalization and dynamic range compression can have on the audio content.

Another reason why loudness control can't simply be left to an engineer is because today's broadcast systems carry far more signals than there are engineers with the time to listen to them. This means that the majority of master control/presentation areas are relying on meters alone, without a pair of human ears double-checking what they are showing. Automated playout systems deliver to the viewer and listener exactly what goes in with no subjective assessment of whether consecutive material has similar loudness.

Everyone in the industry knows that it is entirely possible to take two audio samples and process one so it sounds much louder, even though both samples will show exactly the same peak levels on a PPM or VU meter. Post-production facilities that mix commercials have been doing this for years, because that's what their advertising agency clients demand. Advertisers want potential customers to sit up and take note of their commercials by making them much louder than the surrounding programs. This trend has forced the broadcast industry to find a way to measure program loudness and not just quasi-peak (PPM) or average (VU) amplitude. It is also forcing the industry to agree on and adopt a common rule to measure loudness so material can still be transferred between broadcasters without massive differences in audio level.

The first step toward a solution came in 2006 when the International Telecommunications Union (ITU) set out its loudness metering recommendation ITU-R BS.1770, an algorithm that measured audio program loudness and true-peak audio level. This standard enables audio programs from various sources to have the same loudness once they have been normalized to a specific loudness measurement. Various TV channels and broadcast associations have made recommendations as to what the reference points should be, and although it is clear that we are unlikely to see a universal standard, it is also clear that the differences between these recommendations are minor.

Since 2006, other initiatives have followed, and some countries have started to introduce legislation to counter the problem. Italy started the ball rolling in 2007 when it set limits on loudness and began threatening to fine broadcasters who didn't stay within them. In July 2008, the UK followed suit by introducing its own guidelines and by handing control of the situation to communications watchdog Ofcom.

Other countries around the world are watching with interest. In September 2010, the European Broadcast Union (EBU) released its preferred parameters for loudness measurement, EBU R128. The core R128 recommendation, and the four technical documents that support it, builds on the foundation of the ITU BS 1770 algorithm and specifications, but it also adds a number of new developments, including a gating method.

The U.S. response to loudness is the Commercial Advertisement Loudness Mitigation (CALM) Act, which has been approved by the House of Representatives and the Senate and signed into law by President Barack Obama. The legislation directs the FCC to provide technical guidelines within one year, and then content distributors, including broadcasters and cable and satellite providers, will have one year to comply; although, a stay of one year will be granted to any distributor who can prove economic hardship. The technical guidelines will come from the ATSC committee that developed RP A/85 and will essentially be an adoption of those parameters.

In light of the CALM Act, American broadcasters are now reviewing the quality of their output, and each of the major networks is working toward implementing a standard as soon as possible.

Complying with CALM

Mike Strein, director of equipment planning and sustaining engineering at the ABC network in the United States, said that, like most large networks, ABC has been proactive in dealing with this issue.

He said the network started by characterizing all the day parts to see where all content, including shows, commercials, promos, etc., stood with respect to the guidelines proposed by the ITU at that time. The network put those guidelines into its program and commercial delivery requirements documents, so the content providers would be aware of changes to its specifications.

The network started working with manufacturers to develop meters that could be simply used by operators that deal with ingesting content all day long, and that could be repeatedly measured and compared with meters used by content providers. ABC also looked at loudness processors and how they might be used as a loudness protection device only, on content such as live material that could not be QC'd or ingested first. Lastly, the network tries to communicate all of this to its stations as they are the license holders and the distributor of content to the viewer.

Strein added that ABC has spent time with its content providers to precisely detail how measurements are done to ensure compliance. He said it's important to note that the CALM legislation is not targeted at program content or quietness. Program providers, especially long form and dramas, take a great deal of effort to produce a show with dynamic range and dramatic effect. The intent of the legislation is not to take away any of the quality that those providers strive to produce, but rather to limit the range in which the interstitial material can alter that experience.

Interstitial content providers — those making commercials, promos, etc. — have a job to do, Strein explained. They want to make viewers stand up and notice their content, and they typically accomplish that task by narrowing the dynamic range and pushing the loudness up as far as can be considered acceptable. With DTV delivery, there are usually no limiters in place, so the full volume of this content is delivered to the home and can be quite jarring. The intent of the legislation is to put an end to that effect. With that in mind, content needs be QC'd and treated in different ways depending on whether it is program or interstitial content, all of which is outlined in the ATSC's recommendation.

Strein said that ABC is installing meters in its Los Angeles facility to monitor loudness. In New York, engineers have written technical quality control notes with specific settings for program and interstitial content. Commercial content is QC'd prior to ingest, and if it is out of compliance, the content provider is contacted and either allowed to submit another version or the content can be corrected locally.

Program content is treated very differently: It is monitored according to the guidelines that are averaged over a much longer time period and take dialog into account

ABC expects to deploy loudness processors that will gently correct loud content that has escaped its ingest process. Again, the broadcaster worked for many months with manufacturers to develop settings that only attack the loud sections and leave quiet material alone.

Logging requirement

The current focus on loudness means that a broadcaster's equipment purchases must be dictated by test equipment adaptability and accuracy. New equipment is coming onto the market that can either meter the output of an audio signal and provide warnings if they go beyond given limits or automatically control loudness and provide alarms when the agreed parameters are exceeded. A crucial element of the forthcoming requirements will be the need to log all content with reference to its loudness and peak levels.

Both broadcasters and manufacturers are worried that too many standards will only increase confusion. What everyone wants is for the relevant authorities to agree on a standard and apply it internationally. Without this, what chance does the broadcaster or program maker have if a program/commercial is being produced for international distribution? Until an international standard for all material has been agreed upon, it will be necessary to process all material for each destination, which will only serve to significantly push up costs. Again, a quality device that can be easily reconfigured with presets will help save on those costs.

Regardless of standards, broadcasters are recognizing the need for technology that helps keep them within loudness guidelines; where they put the control is up to them. They can either install equipment that warns them when they are exceeding the limit, or they can install equipment that physically prevents them from transmitting anything that is too loud. Whatever they decide, the only way to future-proof their equipment is to make sure it can be updated, through the addition of either new hardware or software. At least then they can accommodate whatever standard ends up becoming the accepted one — whenever that decision is finally made.

Richard Kelley is sales and marketing director for DK-Technologies.