What Is Loudness? Loudness is a perceptual quantity that can be understood as the degree of the physiological effect produced when a sound stimulates the ear, and it is dependent on factors including bandwidth, frequency, and duration. In digital television delivery, variations of more than few dB are considered objectionable and can lead to viewer dissatisfaction and complaints.

The Origin of the Loudness Problem Because of its much greater dynamic range than analog sound, digital sound has changed the way that broadcasters approach loudness measurement. Peak metering techniques were effective for leveling analog audio content, with its dynamic range limited at the upper end by modulation limits and adjacent channel and at the lower end by the noise floor, and all program elements were perceived at similar levels. A commercial’s loudness simply wasn’t the issue it is today. Today, advertisers have taken advantage of digital audio’s extended dynamic range to push commercials into the headroom portion of the audio, thereby increasing the perceived loudness of those commercials in order to grab viewers’ attention. While peak metering still helps broadcasters to level the audio according to peaks, it fails to address the higher perceived level of loudness in commercials.

Loudness Measurement Methods Audio levels traditionally have been measured according to VU (volume unit) and peak program meter, but neither of these measurements accurately indicates the effect of digital audio content on the human ear. Filling this void and preparing the way for more effective measurement and, ultimately, regulation of loudness was the original ITU recommendation (ITU-R BS.1770), published in 2006. Addressing the subjective nature of loudness, the ITU BS 1770-1/2 (LKFS gated) specification lays out an algorithm for defining levels of measurement according to loudness, rather than peaks. The ITU specification states that higher frequencies are perceived as louder, or more irritating than normal frequencies (from 100 to 1 kHz), and thus assigns frequencies above 1 kHz a shelf amplification of up to 4dB. Recognizing that the opposite is true for lower frequencies, the specification assigns it shelf amplification up to 3dB. K-weighting is the sum total of these two effects, and this value provides the curve used to weight frequencies according to viewer’s perception of loudness. The result is displayed as “LKFS” (Loudness, K-Weighting, referenced

to digital full scale). For relative measurements, loudness units (LU) are used with 1 LU is equivalent to 1 dB. Loudness Regulation Across the World

Government and regulatory bodies across the world have taken up the issue of loudness. In the United Kingdom, the BCAP (Broadcast Committee on Advertising Practice), which went into effect at the start of 2009, limits program and advertisement loudness. That same year in Italy, where Autorità per le Garanzie nelle Comunicazioni (AGCOM) regulates loudness based on the customer experience post-set-top-box, legislation was passed requiring broadcasters to monitor loudness and maintain a log for public inspection. The CSA in France imposes tiered enforcement guidelines with maximum measurements and tolerances specified for both short-form and long-form content. In December 2009, the United States adopted the recommendations put forth in the document “ATSC A/85:2009 Recommended Practice: Techniques for Establishing and Maintaining Audio Loudness for Digital Television.” Based on BS.1770-1, it differs to ITU specifications by defining a threshold of -24LKFS. In August 2010, the EBU released “EBU – Recommendation R 128 Loudness Normalization and Permitted Maximum Level of Audio Signals,” a document that extends and refines the ITU-R BS.1770 specification, particularly with respect to program and channel loudness. ITU-R BS.1770/1 thus emerged as the reference point for broadcasters worldwide. It is, for example, the foundation for the ATSC’s A/85 “ATSC Recommended Practice: Techniques for Establishing and Maintaining Audio Loudness for Digital Television,” where it is referenced for the calculation of subjective loudness for a multichannel audio program in units of LKFS (Loudness K-weighted relative to Full Scale) representing perceived program loudness. Within the United States, the growing discontent with wide variations in audio loudness led to the passage of the CALM bill (Commercial Advertisement Loudness Mitigation Act) passed in December 2010. Intended to prevent commercials from being louder than the programs they accompany, CALM specifies that the rules will apply to TV broadcasters, cable operators, and satellite services. This legislation directs the FCC to incorporate the ATSC A/85 Recommended Practice into the rules, making it mandatory. Enacted in March 2011, ARIB TR-B32 is the standard as defined by the Association of Radio Industry and Businesses in Japan. Like ATSC A/85 in the United States, it is based on BS.1770-2 and defines the threshold as -24LKFS (absolute gate at -70LKFS, -10LU relative gate, 400ms sample blocks). In September 2011, Canada’s CRTC (Canadian Radio-television Telecommunications Commission) announced the “Broadcasting Regulatory Policy CRTC 2011-584,” which directs broadcasters and television service providers to adopt ATSC A/85. A/85 dictates that when loudness of short form content (e.g., commercial advertising) is measured, it be measured in units of LKFS, including all audio channels and all elements of the soundtrack, over the duration of the content. In what has been called the “Golden Rule” for those broadcasters relying on AC-3, the recommended practice says that loudness must match the dialnorm setting of the inserted AC-3 audio stream. The dialnorm parameter is AC-3 metadata that helps in matching reproduced audio volumes when switching between audio program sources. (It can be used in the decoder to adjust and normalize the reproduced audio

level up to 30 dB.) This approach ensures that the reproduced audio level at the viewer’s set-top box (the AC-3 decoder) reflects the level intended by the content producer. For systems not using the AC-3 codec, the loudness of the inserted short-form content must match the delivery channel’s loudness target value within +/-2 dB.

The Elements of Loudness Measurement As broadcasters move to implement loudness measurement, they encounter a variety of terms and concepts that help to define loudness more specifically. For example, the term program loudness describes the long-term integrated loudness over the duration of a program, and it typically is measured with a meter compliant to ITU-R BS.1770 with the addition of a gating function. The gate (an algorithm) effectively pauses the loudness measurement when the signal drops below a certain threshold, thereby ensuring that programs with long periods of silence or low-level background noise will not get too low a value for the integrated loudness level and, in turn, be too loud when broadcast. For audio leveling, -23 LUFS (-8 relative gate) is the target level. The loudness range (LRA) descriptor quantifies in LU the variation of the loudness measurement — excluding the extremes — for a commercial, or any other piece of content. By describing the difference between the loudest and quietest levels in a commercial or other sample, this measurement helps the broadcaster to determine if the content’s audio signal must be compressed in order to match the programming that will surround it. LRA is calculated in 3-second overlapping blocks with an absolute gate value of -70 LUFS and a relative gate value of -20 LU. The loudness of the remaining blocks is then calculated, with the resulting loudness range being the difference between the loudness of the 95th percentile and the 10th percentile. True peak level is an absolute measure used to describe an audio signal waveform’s maximum positive level, which may be 3 or more dB higher than the sample peak level of the same signal. This measurement is valuable in that it provides an estimate of the headroom that is required to handle a signal without clipping.

Compliance Within the Monitoring Workflow Given the pressure of the current regulatory environment, loudness monitoring should be a component of any broadcast, cable, or satellite operator’s approach to signal and service quality assurance. The monitoring systems, already employed across these operations for standards-based verification of audio and video performance metrics on all channels simultaneously, have evolved to include loudness monitoring according to the ATSC A/85 Recommended Practice and “Golden Rule.” Rather than scramble to identify and install effective loudness measurement and monitoring tools, broadcasters and other operators can work with one comprehensive solution that continuously logs and monitors loudness based on EBU guidelines, assists in troubleshooting and mitigating complaints, and provides a clear affidavit of compliance for regulators. The combination of logging and continuous loudness measurement not only helps broadcasters to avoid fees and penalties but also to deliver the highest quality of experience to their viewers. Together, these functions also are invaluable as a tool for identifying noncompliant content and sharing the result with the content provider. Ideally, the monitoring and logging system can capture and store an array of individual loudness measurements, tied frame-accurately to video, for any number of channels. Whether the content

in question aired yesterday, two days ago, or a month ago, a logging system equipped with loudness measurement and reporting capabilities offers immediate assurance of compliance without the need to re-run and sample broadcasts for loudness levels. To play an effective role in supporting loudness compliance, the monitoring system should be equipped to measure AC-3 dialnorm levels and should accommodate global industry loudness specifications and regulations, including ITU BS.1770-1 and BS.1770-2, ATSC A/85 RP 2011, CALM Act, EBU R128 (Tech 3341/2), and ARIB TR-B32. The system should measure momentary (M), short-term (S), and integrated (I) content with adjustable short-form (<2 minutes) and long-form time frames that make it easy to compare an ad’s loudness to surrounding channels. For both compliance and ad verification applications, the ability to provide daily as-run logs of all ads aired and key loudness data for those ads makes it easy to navigate through logged content and respond to a consumer complaint or regulator query. The broadcaster can quickly locate and export both audio and video, with the real-time loudness parameters burned into the video, in a very convincing A/V affidavit.

Volicon Overview One system that offers this functionality is the Volicon Observer, engineered to record aired A/V content 24 hours a day with plenty of capacity to measure loudness and store metadata, as well. What makes this solution stand out is not just the simplicity with which users can launch and maintain loudness monitoring, but also the immediacy of loudness data, whether for live or recorded content. The Observer’s loudness measurement, combined with frame-synchronized content and measurement logging, delivers unambiguous results when the time comes for troubleshooting or validation. For a variety of monitoring applications, Volicon offers an Observer system — and complementary modules — that meets its requirements. While the loudness monitoring module for Observer aids in ensuring compliance, easing complaint mitigation, and avoiding costly legislative penalties, Volicon’s content matching, producer, Observer mobile, and NAVE modules add further value by, respectively, automating broadcast asset monitoring for competitive and licensing purposes, enabling broadcasters to integrate content repurposing into their existing video production chains, allowing authorized users to access logged content on Apple iOS devices such as the iPad and iPhone, and ensuring proper transmission and delivery of NAVE codes to Nielsen monitoring equipment. Contact: Volicon, Inc. 111 South Bedford Street Burlington, MA. 01803 USA +1 781 221 7400 info@Volicon.com