What is loudness?

As someone who has engineered for almost ten years, one of the hardest concepts in sound engineering I struggled to understand early on was that volume (or level) and loudness are two different things. Volume (or level) is something that you can attach a numerical value to, whether it’s 1–30 on a car system, or –2.5 dBFS on a DAW channel. Loudness is something different, it's a perceived volume. For example, you can have two mastered tracks, both of which have peak volumes of –0.4 dBFS, but one can appear louder than the other (loudness can be attributed to RMS, but it doesn't give you the full picture of loudness). This is because you’re perceiving differences in the way that these tracks have been mixed: a well-balanced mix will seem louder because of its frequency content, balance and stereo image.

In the current music market, the loudness of a song does have an impact on how your music is received by your audience. Musicians and engineers have spent the last 30 years competing for the loudest record, in what's known in the industry at "The Loudness War". As somebody who produces and engineers music, I can say that the loudness war is still very present in the industry, with engineers pushing the perceived level of music to superlative levels. Across all genres the same rule applies: if your record isn't loud enough, it won't have an impact on the listener and will not be played by a DJ's or picked up by record labels. Mastering is also very important for loudness but you need a stand-out mix for mastering to produce the desired results.

What produces loudness?

There is no single answer for this, as loudness is the result of combining a few different techniques. One way to increase the perceived loudness of a record is to increase the stereo image of your mix, especially in the higher frequencies, which is the differences between the left and right channels of the mix. This gives the sense that your mix is louder without increasing the overall peak value. Plugins like the SSL Fusion Stereo Image or the Stereo Savage can do that.

Compression will reduce the dynamic range of tracks in your mix, which work by bringing up the lower elements in a track closer to the volume of the higher elements in a track. This evens out the volume of track and allows you to hear the quieter parts of a track or recording. Plugins like the Fab Filer Pro-C 2 are my go to compressors for all around compression, or if you’re looking for something with a bit more character and to introduce some subtle harmonics then try the PSP Vintage Warmer 2.