Loudness Metering Evolved
Since the invention of the initial TT Dynamic Range meter, things have improved in the global audio metering marketplace. We now have world standards for True Peak, Loudness and Dynamic metrics, defined in ITU BS 1770 and applied in practice thanks to the European Broadcasting Union’s R128 and the Advanced Television Systems Committee’s A/85 standards. Though designed for broadcast audio, this has had a huge impact on the whole world of production and distribution, not only broadcasting. Amazingly, we have reliable, predictable and globally interoperable algorithms and parameters, bringing “Loudness Normalization” even into the world of global music distribution.
Who Needs DR Metering?
We had to ask ourselves, “Does the world really need the DRMeter anymore?” The clear answer is, “Fer sure, dude!” Why? Because LRA or Loudness Range, as specified in BS.1770-4, aims to reflect the dynamics of broadband material being distributed by television broadcasters. The LRA algorithm excludes the top 5% of the dynamic band, which is uninteresting for broadcasters working with generous headroom. However, that same top 5% of the whole dynamic range capacity of a system, is essential for music as its content happens almost exclusively in this upper 5% region. DR is the only algorithm for measuring the dynamic integrity of music releases.
Metering For Normalization Targets
Spotify, iTunes, YouTube, TIDAL, Pandora and many other streaming platforms are working with Program Loudness, along with TV broadcasters worldwide plus an increasing number of set–top boxes, SVoD and OTT providers (streaming video services like Netflix, Amazon, Hulu and HBO Go) and even traditional radio broadcasters. iTunes Music and iTunes Match uses a proprietary algorithm which is pretty close to Integrated Loudness mentioned above. We really don’t need another player in the field of Loudness normalization, but we do need a universal yardstick for dynamic density; the DR Dynamic Range algorithm.
DR is a tool not only for pro audio peeps but your audience as well, especially audiophiles, since DR is used by music enthusiasts to judge and compare the provenance of music releases. Our DR database records the values of tens of thousands of songs and albums, so the public can compare different releases and remastered versions.
What About PLR?
Lately, there are plenty of meters showing PLR or Peak–to–Loudness Ratio, the difference between Peak and Loudness values. Wouldn’t this be a good alternative? Nope, because PLR has been defined by broadcasters to reflects the True Peak–to–integrated Loudness Ratio. This makes sense for broadcasters dealing with a minimum True Peak headroom of 1 dB (R128) or 2 dB (A/85). That said, using PLR for music makes no sense because many masters show True Peak overs of up to +3 dB, and information above 0 dBFS encodes latent distortion but not dynamics or loudness. A better alternative would be PSR or Sample Peak (SPPM)–to–Short–term Loudness Ratio. PSR has been defined in the AES Convention e-Brief 373. In order to deliver a complete metering solution, we have integrated the PSR algorithm into DRMeter MkII so that you can compare PSR with DR.
The major shortcoming of PSR is its inability to consider macro dynamics due to the absence of gating and the like, which leads to a higher misrepresentation of dynamic density. So, songs with high macrodynamic would measure far louder. Also, interpretation of values is impossible unless you know the inherent macrodynamics. As an example: Say you have a song with an acoustic guitar intro and a very dynamic interlude but a chorus crushed into “toothpaste,” the PSR would give us a moderately high value due to the dynamic intro and interlude. This is solved with DRM2, as you can actually measure the lack of dynamic range while you hear it.
The Measurements
- The DR bar graph of DRMeter MkII is the same as the original TT DR Meter plug–in and MAAT’s DRMeter. If you want to get a quick sense of the final integrated DR (DRi), you have now two options: Go to the loudest sustained part of a song, often the chorus, and read the numeric value above the bar graph. It will be quite close to an integrated DR measurement, which you’d get from our DROffline batch utility. The new option is to use DRM2’s exclusive DRi function. Run the chorus of your song to get a quick estimate of the official DRi. When you’re done with a track, run the whole song and stop playback. The official integer DRi value will be displayed at the bottom of the DR bar graph. This inclusion of DROffline’s functionality will make your work day go faster!
- The emerging PSR measurement method displays the current Peak–to–Short–term Loudness Ratio for those who want to have a comparison or reference. For the sake of harmonization with existing standards, it makes sense to use Short–term for Loudness measurement, and SPPM (Sample Peak Program Metering) for the PSR peak measurement.
Be careful: With no standard, PLR measurements are not harmonized. So, different manufacturer’s meters display varying results, with each showing its own interpretation of the same audio source. Many use RMS instead of Short–term LU. The difference between PLR and DR is simple: PLR is the difference between peak and average, and is not standardized, while DR is always, repeatably DR. Also, DR ignores low amplitude information, so called “background loudness,” for the sake of a more predictable measurement result. Plus, the DR algorithm also incorporates additional processing for meaningful measurement of the dynamic integrity and dynamic density of popular music.
- LRA or Loudness Range was designed to reflect the deviation of loudness events primarily for broadcast applications. Unfortunately, LRA isn’t ideal for evaluating Loudness of pop and other styles of music since most of recorded music happens in a range of amplitude which is ignored by the mandated LRA algorithm. So, for universality, we have included LRA for broadcast engineers and those who want to be more familiar with metering standards and their applications. The LRA meter allows you to compare results with both DR and PSR.
