WRITTEN BY BRAD MEYER
SOUND EFFECTS EDITOR, BOOM BOX POST
A few weeks ago, we wrote a blog post about how the human ear works, and that inspired me to dive deeper into the section about the brain; specifically, psychoacoustics. The study of psychoacoustics, as defined by Merriam-Webster, is “a branch of science dealing with the perception of sound, and the sensations produced by sounds.” Essentially, psychoacoustics is how your brain perceives sound, and if used correctly, it can be an incredibly powerful tool in a sound designer’s arsenal.
Knowing how to manipulate an audience using sound can come in handy for a number of reasons. For example, a horror film with no sound would not be scary at all, and there is a reason why a well-placed sound build can help make a jump-scare in a horror film so frightening. There is a reason why the sounds of nails on a chalkboard or a shrieking fire alarm are incredibly irritating to most people. It is because sound is one of the most animalistic human senses. Artistically, it can help build suspense, or add fear, happiness, confusion, or even discomfort. Practically and technologically, it can be used to target a specific part of what the audience is hearing. It can take years to understand the entire study of psychoacoustics, but I would like to use this blog post to show just one small example of how, as sound designers, we can use psychoacoustics to our advantage: psychoacoustic bass.
When referring to a film mix, LFE (Low Frequency Effects) is a great resource for adding some meat to a good punch, explosion, or impact, and often bears the brunt of the extremely low end (120 Hz or less) in your mix. In a theater, an LFE is enormous, because to create sounds that low, the mechanism from which they are produced needs to be quite large. It’s the same concept behind why a cello produces a lower sound than a violin: the bigger it is, the lower it can go.
But what if you are not necessarily mixing for the theater? Or you know that the majority of listeners will be listening to the final product on their phone, for example? A television or computer can only go so low, and a phone or iPad could never produce those frequencies even if they tried. There are a number of great plugins on the market, such as Waves MaxxBass that can “boost” the bass for you, and it is described as “[stimulating] a low frequency auditory sensation without the need to produce the whole low frequency range.”
It is worth noting that with a little bit of knowhow and $0.00, the same effect can be created using a simple EQ. The trick is that since an LFE produces somewhere around 120 Hz or less, you can use the harmonics of any frequency below that line to trick the listener into thinking they are hearing that tone. It isn’t foolproof, and will definitely never beat the real thing, but is handy when there isn’t the luxury of an LFE. Let’s say, for example, you have an explosion or large impact sound where most of the low end sits somewhere around 60 Hz. That means the natural harmonics of that would be 120 Hz (2nd harmonic), 180 Hz (3rd harmonic), 240 Hz (4th harmonic), and so on.
Below, I have taken two short parts of sound builds that I have previously done, and used this technique to show how you can “boost bass” using psychoacoustics. In both cases, a good chunk of the low end sat around 50Hz. To exaggerate the effect of having no low end for this exercise, I cut off everything below 350 Hz. Then, I used the knowledge that the harmonics following the original low-end tone of 50 Hz would be 100 Hz (2nd harmonic), 150 Hz (3rd harmonic), and 200 Hz (4th harmonic), and amplified each of those frequencies by 12 dB (to exaggerate for the purpose of this exercise) to illustrate how the power of psychoacoustics will make you think you are hearing the original tone of 50 Hz without ever actually recreating a tone that low.
You can find the original, no LFE, and “bass boosted” versions of each build below!
Main image by DasWortgewand.