The Haas effect is one of the curious psychological effects used by the music and audiovisual industry. The Haas effect is a psychoacoustic phenomenon discovered by Dr. Helmut Haas in 1949. Also known as the “priority effect,” the theory says that when one sound is followed by another with a delay of approximately 40 ms or less, both sounds perceive as one sound.
This refers to how a person determines spatial location through sound. Since the two sounds are treated as one sound, the delay between them is very short, so the spatial position is determined by the first audible dominant sound, regardless of where the second sound is directed. A person determines the source based on what reaches the ear first.
The Haas effect also states that when the same sound reaches the system with a difference of 50 and 100 ms, reflections will be perceived that will give a sense of dimension and sound depth. When the difference goes beyond 100 ms, these will be perceived as echoes.
Stereo music equipment is a revolution because the sound quality is so much better, especially when using headphones. The jump from listening to mono music to listening to stereo music is huge.
Haas effect in music production
The Haas effect, is widely used in the recording industry and music production (sound design also). You may have noticed that sounds with very short delays create a sense of space, while sounds with longer delays provide noticeable repeatability and a greater sense of directionality.
If you’re looking for cool tricks to add to your mixing arsenal, try experimenting with the Haas effect. As we pointed out earlier, a very short delay time, called the Haas effect, creates space, while longer delays give us clearly audible repeats.
Start by dubbing a mono audio track (for example take a hip-hop drum loop or a vocal sample). Move one to the left, the second to the right channel. Then just add a little delay to one of the tracks. You’ll get different results, so it’s best to try until you find an acceptable effect. The task is to make the mono signal wide, like a full stereo. The volume of one of the two sources can also be lowered by a few decibels. So you’ll still appreciate the power of the Haas effect.
A delay of about 5 ms on a track will really improve the directivity and give it an “out of phase” sound, but this is not what we need. For example, if you delayed the left-panning channel for 5 ms, the sound on the right-panning channel will be louder. Up to a certain point, the added delay will further increase focus. However, as soon as you get past 10 ms or so, your two mono tracks will sound wide enough without switching to any channels.
In all cases, the basic rule is to keep the delay time below the echo perception limit of our ears (approximately 35 to 50 ms – no more than 100 ms).
Forget that reverb tends to push instruments into the background and adds depth to your mix. Using only your early reflections, you can strengthen early transients for a more powerful attack (for example, in a drum track as in the image above).
Many DJs use this effect to add depth to their mixes, in addition to playing with the echoes and the volume of their compositions. Thus, they can make the tune they are playing feel closer or further away, in addition to playing with the perceived position of the speakers.
Familiarizing yourself with Precedence and Haas psychoacoustic effects allows you to experiment with innovative new mixing techniques. The next time when you are in the studio and start producing a new hit you will surely pay more attention and use the Haas effect to take tones and melodies in different directions, dimensions, or more intense and deep stretches… The possibilities are limitless…