How Do You Measure Loudness?

We all want our tracks to sound loud. But have you ever stopped to ask yourself: how loud is my song?

It’s a simple question, but I would need more info before I can answer. Why? Because “loudness” can refer to a variety of different things, depending on the context. It could theoretically mean any of the following:

  • How loud the song is at max volume
  • The average loudness of the whole song
  • The average loudness of a section of the song
  • The perceived loudness of a song

This is why there are so many different ways to measure levels: each is designed to measure a specific characteristic of the signal. 

Peak, True Peak, RMS, LUFS – I’m sure you’ve all heard these terms thrown around. While they all measure gain, each does so in a different way. Therefore, it’s imperative to learn what the different measures of loudness are and how to use that information to better our mix.

Let’s jump in.

Point in Time vs. Integrated (Average) Reading

There are two main types of loudness measurement:

  1. Point in Time: measure the signal level and a specific point in time – how loud is the song RIGHT now?
  2. Integrated: measure the AVERAGE signal level over a given time period – how loud is the song in general?

Peak and true peak are point in time. They measure the signal level at a specific point in time.
LUFS and RMS are integrated. They measure the AVERAGE signal level over a period of time.

This is the most important thing to understand:

  1. Peak and True Peak: tell you the volume at a specific point in time
  2. LUFS and RMS: tell you the average loudness over a specified time

Peak and True Peak: Point-in-Time Loudness Measurements

Peak: the maximum level that a signal reaches – the “loudest” point in your signal.

To be honest, we don’t really care that much about peak in today’s world of floating point DAWs. The only thing we need to be aware of is that the PEAK level on our master should not eclipse 0.0 dB. It’s fine if you are in the red (peak of over 0.0 dB) on individual tracks but make sure that your master Peak stays at or below 0.0.

True Peak: the maximum level that a signal reaches – the “loudest” point in your signal.

True Peak is just a more accurate version of peak. It essentially measures peak but at a more detailed level. I can get more into the technical difference, but it really doesn’t matter. They measure the same thing: the maximum level your signal reaches. Using either is fine, but if you have a choice technically True Peak is more accurate.

RMS and LUFS: Integrated (Average) Loudness Measurements

RMS: the average loudness level of your signal over a given time period using the average power of the signal.
LUFS: the average loudness level of your signal over a given time period based on human perception of loudness.

As we know: both RMS and LUFS are integrated loudness meters. This means that they measure loudness over a period of time. The difference is how they measure loudness:

RMS: judges loudness based on the voltage of the signal.
LUFS: judges loudness based on how humans perceive loudness.

I bet that you can guess which one is better. 
Yep, it’s LUFS. It’s the industry standard, and for a reason.

Since LUFS measures average loudness based on human perception of loudness, it gives us a more accurate representation how loud our listeners will judge the loudness of our tracks. This perceived loudness is what we care about. Our listeners aren’t going to be putting metering plugins on our tracks to judge loudness, they’re going to be listening to them.

It’s worth mentioning again: LUFS is the industry standard. This alone is another reason to use LUFS. It will be more seamless when preparing tracks to send to streaming services and other platforms if you’re making mix decisions based on LUFS measures. Don’t worry: if you only have access to an RMS meter, that’s fine. A LUFS meter and an RMS meter will give you very similar readings. But if you have an option, I would use LUFS.

The Loudness Wars

The loudness wars are over. It’s settled. The streaming platforms ended them – this is how:

We know that LUFS measure the average volume of a song over time. What the streaming platforms did was implement a maximum LUFS reading for your track as a whole. As part of the submission process, these services will run your track through their LUFS meter and turn it down if the LUFS level is too high. Thus, there’s no incentive to make your track as loud as possible; the streaming services will just turn it down.

Here is each platform’s maximum LUFS limits:

Best Metering Plugins

Now we understand the difference between Peak, True Peak, RMS and LUFS, and we know exactly how loud to make our masters for export to the major streaming services. Now it’s time to get ourselves a metering plugin, start measuring our loudness, and use that information to make better decisions in our mix.

The following are (in my opinion) some of the best options:

  1. Youlean Loudness Meter 2 – best free option
  2. ADPTR AUDIO Metric AB – amazing referencing tool that has metering built in. I love this thing.
  3. Waves WLM Plus Loudness Meter
  4. FabFilter Pro-L – a amazing limiter that has a ton of metering tools built in
  5. LEVELS by Mastering in the Mix