The CALM Act and loudness measurement standards


Lack of standards for digital audio recording has resulted in recordings with widely varying audio levels. Listeners would prefer audio content to have consistent loudness levels, and become annoyed by inconsistencies. In the broadcast industry, advertisers attempt to grab attention by manipulating loudness, and loudness issues are a major source of viewer complaints.

Interestingly, listeners show broad agreement as to the loudness of audio programming – and whether it is too loud. However, devising an objective metric for loudness has been a challenge. There have been a succession of standards and recommendations, from multiple organizations, addressing the issue.

In the US, the issue has taken on greater urgency with the passage of Commercial Advertisement Loudness Mitigation Act (the CALM Act) to address consumer complaints about loud commercials.


ITU BS.1770

The original ITU BS.1770 standard, issued in 2006, specified “audio measurement algorithms for the purpose of determining subjective programme loudness, and true-peak signal level.” It was motivated by the observation that listeners prefer audio programs to be of consistent perceived loudness, and by the lack of measurement methods that could provide an objective estimation of this subjective loudness.

The standard was revised in 2007 as BS.1770-1, and again in 2011 as BS.1770-2.

EBU R128

The European Broadcasting Union (EBU) also studied the needs of audio signal levels in production, distribution and transmission of broadcast programmes. The result of their work was published in 2010 as Recommendation R 128, with accompanying Tech Docs 3341, 3342, 3343 and 3344. It adopted BS.1770 for loudness measurement, and supplemented it with true peak and loudness range measurements, and metering requirements.

The EBU standards effort identified the need for a gated measurement of program loudness, and this requirement was reflected in revisions to the BS.1770 standard.


In November 2009, the ATSC released recommended practice A/85: Techniques for Establishing and Maintaining Audio Loudness for Digital Television. It “focuses on audio measurement, production, and postproduction monitoring techniques, and methods to effectively control loudness for content delivery or exchange.” This document adopted BS.1770 as the basis for loudness measurement.

Legislation and regulation

In the US, consumer complaints about loud commercials prompted legislation in the form of the Commercial Advertisement Loudness Mitigation Act (the CALM Act). It was signed into law in December 2010.

The CALM Act directs the Federal Communications Commission (FCC) to prescribe a regulation limiting the volume of television advertisements transmitted by a television broadcast station, cable operator, or other multichannel video programming distributor. The act directs the FCC to incorporate the recommendations of ATSC A/85 and its successors in the regulation.

In May 2011, the FCC issued a Notice of Proposed Rulemaking for the act and solicited comment. This was followed, in December 2011, by a Report & Order adopting rules to implement the CALM Act which take effect on December 13, 2012.

Qualis Audio's position

Qualis Audio responded to the FCC's solicitation for comments with suggestions that we believe will reduce the risk that Commission rules will unduly burden any individual entity while achieving the result envisioned by Congress when the CALM Act was passed.

We believe the industry will best be served by enforcement rules which recognize the learning curve faced by regulated entities and by the industry at large. We are concerned that an overly hasty response will eliminate loudness complaints at the expense of the audio quality improvement digital television offers consumers, while a more measured response can maintain a better overall experience for consumers.

Related documents

The Commercial Advertisement Loudness Mitigation (CALM) Act

The CALM Act (H.R. 1084/S. 2847) legislation as passed by Congress and signed into law by the President. Certified by the Superintendent of Documents, US Government Printing Office.

>PDF format, 2 pages, 04-Dec-2011

FCC Report & Order adopting rules to implement the CALM Act

The FCC document specifying the rules adopted to implement the CALM Act legislation. The rules apply to digital TV broadcasters, digital cable operators, and other digital multichannel video programming distributors. They describe how the FCC will rely on a pattern of consumer complaints as an indication of possible noncompliance and cause for investigation, and the steps broadcasters must take to be deemed in compliance. For content passed through from producers, the rules also establish a “safe harbor” to establish compliance. The rules take effect on December 13, 2012.

>PDF format, 62 pages, 13-Dec-2011

FCC CALM Act Notice of Proposed Rulemaking

The FCC document describing their findings concerning implementation of the CALM Act legislation. Contains several dozen questions to industry and the public concerning implementation details, documentation requirements, forfeiture process and amounts, etc.

>PDF format, 37 pages, 27-May-2011

Qualis Audio’s Comments on the FCC CALM Act NPRM

Qualis Audio’s response to the FCC NPRM, containing suggestions for how to interpret phrases in the Act, what the FCC should require as evidence of compliance, how to handle complaints, how to implement forfeiture, etc.

>PDF format, 18 pages, 5-Jul-2011

TechNote 1: Loudness Measurements and the CALM Act

The recent passage of the CALM act has made loudness management a major concern for broadcasters and those that supply them with programming and advertising. Most broadcasters and content creators understand that compliance will come at a cost, in capital expenditures, changes in their workflow and additional record keeping in the form of logs and reports. However, before investing in any equipment or process it is essential to understand the legislation and its likely implications. This note explains the CALM act and its ramifications, and suggests cost effective solutions to conformance issues.

>PDF format, 6 pages, revised 31-May-2011

TechNote 2: Understanding & Verifying Loudness Meters

Explains the ITU BS.1770 loudness measurement standard, how it has changed and how to verify that a loudness meter meets its requirements. Also see the accompanying Loudness Meter Test Suite.

>PDF format, 7 pages, revised 31-May-2011

TechNote 4: Loudness Variation When Downmixing

The loudness of surround format programs is generally assessed assuming they are reproduced in surround. Unfortunately, as explained in the technical note, program loudness may change considerably when reproduced in stereo.

>PDF format, 7 pages, revised 06-May-2013

TechNote 8: Automated Control of Loudness Measurements

Loudness measurements conforming to ITU BS.1770 must start and stop coincident with the beginning and end of the program or commercial being measured and be suspended when breaks occur in the program. The Sentinel provides this capability, and includes a mode which automatically measures both the program and interleaved commercials. This may be controlled manually through the browser interface, via logic level hardware inputs, or by software via the network interface. This note describes the control methods available for automated applications.

>PDF format, 4 pages, 13-Jul-2011

Loudness Meter Test Suite

Supplemental material for TechNote 2: Understanding & Verifying Loudness Meters. This test suite will be evolving – check back periodically for updates.

>WAV files in ZIP archive, 15.5 Mb, revised 12-May-2011

Loudness Monitoring
Broadcast Engineering, Feb 1, 2011

The ITU BS.1770 loudness measurement standard is changing. Here’s what you need to know.

By Richard Cabot and Ian Dennis

>HTML format

Prism Sound / Qualis Audio Webinar: Is Your Loudness Meter Compliant?

Implications of the CALM Act. Delivered by Doug Ordon and Rich Cabot

>MP4 format, 152.4 Mb, 21-Apr-2011