Haas Effect / Precedence Effect

The Haas effect and the precedence effect are effectively two names for the same psychoacoustic phenomenon and can be used interchangeably for the most part. Haas refers to Helmut Haas, the scientist credited with first describing this effect, while precedence provides a better sense as to what the effect actually is. I did explore some psychoacoustic phenomena during my first semester studies, but decided to put off study of the precedence effect until now due to its relevance. The precedence effect is a fundamental reason that we are able to perceive sound dimensionally, which relates directly to my previous post about stereo imaging.

The precedence effect occurs when we hear an initial sound and then its reflections (echos/delays, reverberations) approximately 1-40 milliseconds later. The information that arrives in our ears during this short period is critical in how our brains determine the location or width of a sound. This is the precedence effect in a nutshell; in reality it is a very simple phenomenon to understand if you do not dive deeply into neuroscience, and within that area there is still much to discover. A basic understanding of this effect can still be very useful for a musician or producer.

The precedence effect, along with stereo imaging, is often used in the mixing process in music production in order to make an instrument sound "wider" or fit better into the mix. By using a delay/echo audio plugin on a single channel, you can add a delay that falls into the Hass range, 1-40 ms. You can adjust this value to help your instrument or sound fall into the ideal place in the mix. It is important to consider the other parameters in the delay plugin and make sure that it is subtle enough to take advantage of the precedence effect without adding unnecessary echo. It is also possible to use the precedence effect to make a mono recording sound like a full stereo recording. This process is described succinctly here.

Works Cited: 

 "Creating Depth: The Haas Effect." MixCoach. Web. 12 Jan. 2016. 

 "Precedence Effect." Simon Fraser University. Web. 12 Jan. 2016.