Recognizing this discrepancy, the International Telecommunications Union (ITU), in about 2003, began work on a new way to measure loudness of commercials and TV program content, they called Loudness-Based measurement. By 2005 a standard was developed called ITU-R BS.1770 and there have been subsequent versions since (it’s now at -4) that made incremental improvements to the standard. The intention was to gain greater consistency of volume across both commercials and TV programs.

The ITU did extensive listener testing to show the correlation of a large number of listeners, and the co-efficient of correlation came out to approximately .98 over a very large range of playback levels and program types. This would indicate that the loudness meter is good at indicating the loudness threshold among all listeners.

“Loudness Based measurement is more refined than a peak reading meter,” said John Kean, an audio engineering consultant and former Senior Technologist at National Public Radio (NPR) Labs, in Washington DC. Kean has traveled the country giving presentations on this relatively new form of audio monitoring. “It includes a filter that replicates the ear’s response to sound volume according to frequency. It also includes an integrated time-waiting circuit, which correlates to the ear’s sense of loudness on the duration of sound.”

He said that by putting those features together users can measuring multiple channels simultaneously because the ITU loudness meter can handle up to 7.1 channels of surround sound audio and provides the tools to combine them together properly before they are distributed. “And it can do it in a rather sophisticated way,” he said.

The ITU recommendation for loudness monitoring is a voluntary recommendation, but the response from major broadcasters that stream content has been excellent. It’s been so successful, that it has been adopted by the EBU (EBU-128 standard) and specifies how European broadcasters use the loudness meter to standardize their content for program exchange—between producers and different countries—and also for their TV system (DVB-T2). It has also been adopted by the ATSC as a solution to meet the U.S. government’s mandate of the Commercial Advertisement Loudness Mitigation (CALM) Act, which went into effect on December 13, 2012. This ITU recommendation is increasingly being used in the U.S., by both radio and TV broadcasters. Using loudness-based measurement, broadcasters can also automate their programs levels to ensure compliance with government regulations.

Last year—with the goal of achieving greater consistency between a commercial and the surrounding program content—the Audio Engineering Society (AES) Technical Committee used ITU-RBS.1770 as the basis for its forthcoming guidelines on how to apply the ITU loudness meter to the production and distribution of programs. It is also being applied to Internet streaming.

“The major fee-based online video content distributors are monitoring their own audio carefully, and are remarkably similar in levels,” Kean said, who worked on that Technical Committee. “The challenge is between them and the vast amount of free content viewed by the public. Part of our goal at the AES was to write guidelines on how distributors could use the ITU loudness measurement to attain that consistency of audio content level.”

The idea of loudness-based measurement is growing in acceptance equally across the radio and TV engineering worlds. As more program distributors learn about it, Kean said, they have begun implementing it as necessary. Presentations like the one he will give at the IEEE Broadcast Technology Symposium, in Hartford, Conn., October 11-13 go a long way toward this industry education.

There are several free and paid software plug-ins now available from companies like Orban (U.S.), Hofa Plug-Ins (Germany), and DP Meter (India). There are also hardware-based versions from U.S-based companies like Linear Acoustic and Wohler Technologies, as well as TC Electronics (Denmark). The hardware models are more expensive, but may provide additional measurement tools, such as program stream history.

“Frankly, what the industry needs is a good, low-cost real-time hardware meter,” Kean said, “but surprisingly, no one has developed one yet.”

The ITU loudness-based measurement spec also accommodates the Loudness Range of a program. This can tell you whether the range is suitable for listening in various environments, like in the car or listening on ear buds. It can also help indicate whether too much processing has been done to the file.

“Very often, you don't need as much processing as you might think,” he said. “This Loudness Range measurement, called LRA, can be a valuable indicator to tell you whether there is a need for any further processing at all. Very often the content you are producing or distributing is just fine the way it comes in. I think that can lead to a greater sonic quality for listeners around the world.

“That certainly has been true in Europe, where programs are now much more consistently level and there’s not that abrupt increase in volume across different programs that you still see from time to time in North America.”

Editor’s Note: The AES Technical Committee, chaired by Jim Starzynski, director and principal audio engineer at NBCUniversal Advanced Engineering, is addressing audio metrics for online video content as well as programs distributed via OTT. The committee has recently completed some initial guidelines for how distributors should handle audio.

“Fortunately, the AES group has a great representation by many major content producers as well as distributors, so I know they will advance the metrics for online and over-the-top video,” said Kean. “At the end of the day using this new way of measuring loudness makes the audio professional’s job easier and ensures a good listening experience for the TV audience.”