Loudness Standard FAQs

Back to top


  • General Questions
  • Producer-focused Questions
  • Station-focused Questions
  • Technical Questions

General Questions

What is “Loudness”?

Loudness is a way to more accurately measure audio levels based on the way humans perceive sound.

In the television, film, and music industries, loudness measurement has become the standard to ensure that audio levels remain consistent and that consumers do not feel compelled to adjust their volume controls depending on the program.

Unlike traditional digital peak meters that reflect only the highest peaks in an electrical signal, loudness meters evaluate audio considering multiple psychoacoustic factors and generate an easy to read numeric value. These measurements are far less subjective than older approaches and enable producers to more easily and accurately produce material at a consistent level. They also facilitate consistency between content producers.

If each producer mixes to the same loudness target, public radio content from myriad sources should have consistent levels throughout the system, providing an improved experience for the listener.

Additional resources and technical documentation about loudness can be found at www.prss.org/loudness.

What is the updated PRSS content submission standard?

The PRSS Submission Standard is -24 LUFS, ± 2 LU Integrated Loudness, with audio peaks ≤ -3 dBFS for Sample Peaks and ≤ -2 dBTP for True Peaks. This means producers should submit their program segments with audio levels at -24 Loudness Units Relative to Full Scale (LUFS), within a range of two Loudness Units, (accounting for unpredictability in live programming), and with no sample peaks above -3 dBFS nor true peaks above -2 dBTP.

Why is the PRSS issuing a new standard?

For several years, PRSS staff have heard from stations that varying audio levels were a problem. In early 2014, D/I Committee member and American Public Media Chief Technology Officer & Head of Music Services Nick Kereakos and NPR CTO Marty Garrison had a discussion about levels and agreed that the PRSS should make content within the system more consistent. A subsequent analysis of material in the system confirmed that audio levels varied widely. Updating the standard and developing feedback tools began in early 2014. Using loudness as the way of measuring levels should facilitate this desired consistency.

When will it take effect?

In January 2015, the PRSS began monitoring audio levels of file-based programs uploaded to ContentDepot. In mid-2015, the PRSS will begin to share the data from monitoring file-based programs with the producers of those programs. Later in the year, data on live streams will be shared as well.

What tools will the PRSS make available for producers to comply with the standard?

The PRSS has collaborated with APM to research and test a variety of loudness metering software and hardware. A searchable, web-based catalog of tools will be made available to producers. This will not be a comprehensive list of all tools but rather a sample of those available.

Is there currently a loudness standard? If so, why is it being changed? If no, why do one now?

There is currently a submission standard. It is being updated to be loudness based, rather than signal level (voltage) based. This is the industry standard, and is much less subjective and more accurately reflects how we hear. The result will be greater consistency for listeners.

What will the PRSS’ role be in instituting the standard?

The PRSS NOC will monitor the loudness and peaks for all programs, file-based and live. If programs are discovered to deviate from the submission standard, the PRSS will communicate this to producers and help them correct submitted content.

Is there going to be any kind of enforcement actions taken for non-compliance?

The PRSS is beginning by monitoring and communicating compliance. After six to twelve months, the PRSS will assess adherence and improvement and then re-assess.

Will the analysis be based on segments or an entire show?

The analysis will be based on segments.

Will the length of a segment impact the measurements?

The length of a segment will impact the assessment of program loudness to the extent that an hour with thirty minutes that are loud and thirty minutes that are quiet will average out to being on target. Therefore, a shorter segment will more likely be consistent at a given LUFS value.

Will speech vs. music vs. sound effects be treated differently?

The standard uses speech as the anchor element to bring consistency between shows and production elements. Show segments will need to meet the standard regardless of content, but using voice as an anchor element brings a consistent experience for the audience.

Will live streams be monitored?

Live streams will be monitored, beginning later in 2015.

Will there be any differences in the standard between LWSFs and file-based programs?

The PRSS standard will be the same for all programs, file-based, LWSFs or live streams

Will promos and underwriting spots be analyzed?

All content will be analyzed, including promos and underwriting.

What do I do if I want to comply with the standard, but I’m unable to purchase new equipment or software?

The PRSS NOC will work with individual producers to ensure program material adheres to the new submission standards. This will include guidance on if the overall levels need to be adjusted to meet the loudness target of -24 LUFS. The ContentDepot Portal will provide loudness measurements for producers who are not able to evaluate their submissions using their own tools.

Additionally, NPR Labs is currently developing a file based loudness normalization tool, which will be free to use by any PRSS customer. This application is slated to be released in April 2015.

How will the implementation of the new standard be monitored?

After the PRSS has run the monitoring and communicating program for a six to twelve month period, it will take a number of steps to gauge the effects. PRSS staff will conduct another analysis of content levels, similar to the work done before the program began. The PRSS will then field another survey to check whether stations have noticed differences in consistency.

Is this related to the CALM-Act?

The CALM-Act (Commercial Advertisement Loudness Mitigation Act) requires the FCC to prevent the audio level of television commercials from being broadcast louder than television programs.

The CALM-Act does not apply to radio broadcasters. However, television broadcasters use similar loudness measuring technologies to reach compliance.

Producer-focused Questions

What will happen if my content doesn’t meet the new standard?

The PRSS plans to allow all producers access to our monitoring data, so that they can see for themselves how well they are complying with the standard. In addition, the PRSS NOC plans to communicate with producers whose content is out of spec. Additional training materials will be provided to help with incorporating an awareness of program levels into production or post-production workflow.

How can I know if I am on-target/in-spec?

Use a loudness tool that is ITU BS.1170-3 compliant. There are a number of ways to integrate loudness tools in the production chain – either during production, post-production (in an audio editor), using file-based measurement, or in-line for live shows.

See the PRSS-distributed tools list for a number of options.

Does this only affect my content that is distributed by the PRSS? What about content handled by another distributor?

Other distributors may adopt this or another loudness-based standard, but this applies only to programs distributed by PRSS.

If I produce local content only, do I need to comply with the standard?

No. This standard only applies to content distributed via the PRSS. However, stations will notice improved consistency between segments and programs if these practices are adopted for all content.

If I produce national content only, do I need to comply with the standard?

Yes. Content delivered to PRSS for distribution needs to meet the standard.

What are the estimated costs of meeting the standard?

That will depend on many factors unique to each producer. PRSS understands that different producers will comply with the standard in different ways and one of the decisions when selecting a metering tool will be the cost.


What is the bare minimum in equipment/software investment I can make and still meet the standard?

This depends on your production method. If you produce a live show, you will need to integrate an in-line meter to monitor the loudness and level of the production. That is best achieved with a dedicated hardware meter, though many broadcast console manufacturers now offer built-in loudness meters. There are a wide range of hardware meters available on the market at varying price points.

If you produce a file-based show, there are a number of ways to ensure compliance. Ideally your workflow will incorporate a number of these options.

  • In production : Record and produce content for your show using loudness meters as if it were a live show. This reduces the amount of adjustment needed and thus simplifies post-production.
  • In post-production : Use loudness meters when mixing content – either hardware meters or software plugins. To ensure that segments meet the spec, hardware meters will require that they are played through from beginning to end to get an accurate measure. Software meters often allow for faster than real-time analysis.
  • File-based measurement : These tools measure audio files outside the audio editor, after the content is mixed and just prior to delivery.
  • File-based correction tools : These tools measure and adjust audio files to meet a loudness spec. They simply apply or subtract gain to the audio to hit the target loudness. While this is the easiest and potentially the cheapest – the bare minimum option – it is not preferred as it can affect the sound of production negatively.

See the PRSS tools list for options.

Will this standard change the way I produce my music-focused program?

The standard will not impact the production quality or style of your program. If you currently mix voice and music elements to be consistent with each other that will not change.

Will this slow down the uploading process?

This will not slow down the uploading process – the assessment of program loudness will be done in parallel to the ContentDepot upload.

Is there a way to see how my show compares to other productions in the system?

No. Producers will only have the ability to see loudness values of programs they are responsible for.

Does this standard apply to podcasts and streaming audio?

The PRSS standard only applies to audio distributed through the PRSS system.  That said, using loudness brings improved consistency to production, which in turn has a strong impact on podcasts and streaming audio.  

The PRSS standard can be used as a starting point for improved consistency in podcasts and streaming audio.  For a technical look at how loudness can be applied to podcasts and streaming audio, see Thomas Lund’s “Audio for Mobile TV, iPad and iPod.”


Station-focused Questions

Is this standard going to affect the sound of the shows I broadcast?

Yes, in a very positive way. While programs will be more consistent with each other, the production quality and style of individual shows will not change.

Stations should be aware that levels for certain programs may shift over the short-term as some content providers change their processes in an effort to move towards -24 LUFS.

Stations should pay special attention to gain adjustments they may have previously put in place in their local systems to combat varying program levels.

Will this affect delivery time of my programs?

This will not affect the delivery time – the measurement of program loudness will be done separately from the upload into ContentDepot.

Will the cost of subscribing to shows be affected?

The cost of subscribing to shows will not be affected. For subscribers, this will result in more consistent content but will not require any changes.

Since the goal of this is to improve the listening experience of listeners, how are you going to gauge whether the new standard is effectively improving consistency?

Throughout 2015, the PRSS will regularly examine the data from loudness monitoring to assess how compliance is changing. The PRSS also plans to send out another survey to stations after the program has been running for a while to determine whether stations notice the situation to be improving.

Is this something we should communicate to our listeners?

Stations certainly have the freedom to do so if the staff feels it would be of value. Listeners appreciate consistency, and if a station wants to promote the consistent audio levels of its programs, it is welcome to do so.


Technical Questions

My production facility uses Durrough meters. Can we use these to comply with the standard?

There are some reports that limited success can be achieved using carefully-calibrated Durrough meters even though they are not ITU BS.1170-3 compliant. This requires a trained engineer who understands the differences and limitations of Durrough meters versus an ITU BS.1170-3 compliant meter.

Is ReplayGain the same thing? How is ReplayGain related?

No. ReplayGain is file-based metadata that informs a gain adjustment in the playback process. It uses a loudness measurement which is not ITU BS.1770-3 compliant. It also incorporates only 14dB of headroom while the PRSS specification has 24dB. Because it pertains to playback only, ReplayGain is not able to be used as a production tool or a distribution guideline.

The specification provides a variance. Should I aim for the target of -24LUFS or is it fine to be anywhere within the variance?

In the interest of consistency between shows and segments you should aim for -24LUFS. The variance is included to recognize the unpredictability of live radio.

Why didn’t you pick the EBU R128 or ATSC A/85 specs I’ve heard so much about? How is the PRSS standard different?

Creating a customized standard is in the best interest of the PRSS, as it allows us to closely match the current peak spec as well as maintain the -3 dB of headroom in the system. Also, given that the goal is to create consistency between programs and segments, it was determined that other specifications were designed for other circumstances, be they television or for radio production with fewer live shows.

The differences between the PRSS standard and EBU r128 are minimal. The PRSS target level is one LU lower (matching ATSC A/85) and the max peak spec is slightly lower.

Is the PRSS standard compatible with EBU r128 and ATSC A/85?

The PRSS standard is ATSC A/85 compliant. The majority of the material produced at the PRSS standard will be EBU r128 compliant.

My facility produces nationally distributed content for public television and public radio. What are the differences (if any) between those two submission standards?

The submission guidelines for PBS and PRSS are very similar. Both organizations use -24 LUFS (LKFS) as their loudness target. PRSS and PBS both specify that True Peak levels shall not exceed -2 dBTP.

What’s True Peak? How is it useful?

True Peak is a specification that uses oversampling peak meters to catch inter-sample peaks which a typical peak meter cannot read. True Peak is included in ITU BS.1770-3 and is found in the majority of loudness meters. You can read more about True Peak here: http://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1770-3-201208-I!!PDF-E.pdf

What is LRA?

Loudnes Range, or LRA, is a statistical analysis of the loudness range of program material. It is included in EBU r128 and is found in the majority of loudness meters. You can read more about LRA here:

The PRSS standard does not specify a LRA value for programs, though it does have uses in troubleshooting and ensuring consistency.

What are Integrated, Short Term, and Momentary Loudness? Are we using them?

These are all loudness measurements over time as specified in EBU r128 and found in most loudness standards. They are all measured in LUFS or LU. Integrated loudness corresponds to the average loudness measurement of an entire program, segment, or file, and includes gating to differentiate between ambient/room tone, silence, and program material. Short Term loudness is the average of a rolling 3-second window and does not include gating. Momentary loudness is the average of a 750ms rolling window that is not gated.

More can be read about these measurements here: https://tech.ebu.ch/docs/tech/tech3341.pdf