• A Comprehensive Approach to Broadcast Loudness

    Inconsistency in loudness levels is one of the most pervasive problems in the broadcast industry. Powerful Dolby tools and technologies help you control broadcast loudness problems and ensure a better listening experience.

    • Preset Metadata

      Metadata in broadcast formats such as Dolby® Digital Plus™ and Dolby Digital ensure that viewers get consistent audio levels and superior sound.

    • Dialogue Measurement

      A technology for accurate dialogue measurement, Dialogue Intelligence™ adjusts volume levels so viewers can hear every word clearly.

    • Built-in Volume Leveling

      Televisions, A/V receivers, and set-top boxes with Dolby Volume correct the differences in volume levels across content types and channels.

    Controlling Broadcast Loudness

    The commercial that blasts like an alarm clock; the scene in which you see the actors' lips move but you hear no dialogue; the channel that always seems louder than the others. If you watch TV regularly, you know these and similar frustrations well.

    Volume inconsistencies are still with us, despite reports to the contrary. The problem has reached the point that governments and standards organizations around the world increasingly mandate loudness control. In the United States, for example, the Commercial Advertisement Loudness Mitigation (CALM) Act took full effect in 2012.

    Regulations can help, but solving all of the problems related to broadcast loudness requires a comprehensive approach—an approach that Dolby embraces with tools and technologies for broadcasters and equipment manufacturers alike.

    The Causes of Loudness Inconsistencies

    Loudness problems can arise during content creation and at many other points in the broadcast chain. These problems occur for many reasons:

    • Programs are often created for different replay environments or mixed in different parts of the world.
    • Content creators may be unfamiliar with setting loudness levels.
    • Traditional PPM and VU meters are not designed to measure loudness.
    • Operators interpret traditional meter readings differently.
    • Signal measurement and loudness have only limited correlation.

    The Consequences of Loudness Inconsistencies

    Poor loudness control can have significant consequences, such as:

    • A degraded experience for viewers
    • Viewer complaints
    • Viewers switching to other channels or providers
    • Regulatory issues

    The Dolby Solution

    What makes the Dolby approach to broadcast loudness effective is that it addresses the full range of causes of volume inconsistency across the entire broadcast chain. Dolby metadata includes tools for broadcasters to control loudness levels and tailor the audio to the consumer's replay environment.

    Measurement tools from Dolby and our partners support international standards that include:

    • ITU-R BS.1770
    • ATSC A/85
    • EBU R128

    And Dolby Volume, our volume-leveling solution for TVs, set-top boxes, and A/V receivers, delivers a uniquely consistent and satisfying entertainment experience.

    Dolby Speech-Gating Reference Code

    Include Dolby technologies in your loudness measurement products at no cost.

    Broadcast Loudness Solutions for Professionals

    Because unwanted loudness variations have no single cause, Dolby offers multiple solutions.


    Control loudness problems with Dolby solutions designed specifically for broadcasters.

    Broadcast Loudness Specifications

    Audio coding algorithm

    Dolby E

    Dolby E program configurations (user selectable)

    5.1; 3×2; 5.1+1+1; 6×1; 5.1+2; 8×1; 4×2; others selectable

    Audio sampling rate

    48 kHz

    Video frame rates

    29.97 fps (NTSC); 25 fps (PAL); 23.98, 24, 30 fps (requires Dolby E Tri-Level Sync Interface DP579)

    Frequency response

    20 Hz to 20 kHz, ±0.25 dB


    <0.01% at 1 kHz; <0.02% at 20 Hz to 20 kHz

    Dynamic range

    >110 dB


    Encoding: fixed, one video frame; PCM delay channel: fixed, one video frame