Dr. Helmut Haas identified the Haas effect in 1949 as a psychoacoustic phenomena. The rule says that when one sound is followed by another with a delay period of about 40 ms or less (below humans’ echo threshold), the two sounds are heard as a single sound.

This has to do with how we use sound to establish our spatial position. Because two sounds with a very short delay are seen as one, the first heard, dominant sound determines spatial location–regardless of where the second originated from.

To summarize, we identify the source of a sound by the first sound that reaches our ears. Any additional reflections or noises that arrive after a brief pause provide the impression of depth and vastness, but they do not seem to be separate sounds.

The Haas Effect in Audio

Take advantage of the Haas effect if you’re searching for new techniques to add to your mixing arsenal. As previously mentioned, the Haas effect creates spaciousness with extremely short delay periods, while larger delays produce distinct repetitions and a stronger feeling of directionality.

We use panning a lot to give our mixes directionality. Using delay, on the other hand, regulates the time of each channel, while pan pots control the volume sent to each channel. Because we humans hear sound based on both intensity and time, using the Haas effect may produce some incredible effects. Here’s how to do it:

How-To: A Haas Effect-Inspired Mixing Technique

This is one way to use the Haas effect to create a larger stereo picture, which allows for a more expansive mix with greater depth. Begin by duplicating a mono audio recording and panning each one hard left and right. Then, on one of the tracks, just apply a brief delay.

Various settings for your delay time provide different effects, so experiment until you discover something that sounds nice to you. But keep in mind that the objective is to make our identical mono recordings seem broader than they are.

A 5 ms delay on one track will actually increase directionality and produce a “out-of-phase” sound, which isn’t what we’re seeking. For example, if you delay the left-panned channel by 5 ms, the sound in the right-panned channel will be more powerful.

The more delay you add, up to a point, the greater directionality you’ll get. However, after you’ve gone over 10 milliseconds or so, your two recordings will sound broader instead of more or less strong in one channel.

The key is to maintain the delay duration below our ears’ echo threshold–roughly 35-40 ms for most people–in order to avoid audible repetitions. You’ll discover that you’ve added depth and expanded the stereo picture of an otherwise “flat” mono recording without using reverb or an imaging plugin!

Other Psychoacoustic Mixing Applications

You may also decrease directional masking in your mix using the same method as before. When panning isn’t enough, we must depend on the time component of our hearing to navigate the stereo field deftly. You may use a stereo delay with one channel set to 0 ms and the other side tweaked to your liking.

We may also “thicken” mix components utilizing the Haas effect’s principles and early reflections from a reverb plugin. Early reflections are within the Haas effect’s range since they often occur far below our ears’ 35-40 ms echo threshold.

Forget about reverb’s tendency to drive components into the depths of the mix abyss. You may thicken up the first transients of a sound without utilizing the reverb tail and just employing early reflections for a beefier, in-your-face assault.

Final thoughts

You may start experimenting with these methods in your work now that you’re more acquainted with the Haas effects and how they’re used in mixing!

Remember that you may use the psychoacoustic phenomena in a variety of ways to get different outcomes. Duplicate a mono recording and pan each hard left and hard right to create a broader, deeper stereo picture. You may improve your stereo image by delaying one channel for 10 to 35 milliseconds. When panning alone isn’t enough to minimize directional masking, the same method may be used.