The history of the Haas effect
The precedence or Haas effect has first been discussed back in 1949 in the works of H. Wallach, E. Newman and M. Rosenzweig in their publication named “ The Precedence Effect in Sound Localization”. The authors discussed the phenomenon in this 1949 paper two years before the publication of the 1951 paper by Haas, “On the influence of the Single Echo on the Intelligibility of Speech”. This was after the precedence effect became also known as “ Haas effect”. The authors point out that in 1930, von Bekesy reported the existence of a precedence effect, “Meaning a suppression or concealment of the sound image which arrives latter”.
Using earphones and loudspeakers, the authors study a time interval over which the fusion of two sounds takes place. The integration interval is between 5 ms for clicks and up to 40 ms for more complex sustained sounds. The localization of the first arriving sound largely determines the localization of the fused sound. It is based on the time difference between the two ears when the two sounds have the nearly same intensity. The authors point out that the precedence effect can be overridden if the later arriving sound is 15 dB or louder than the first sound.
You can observe the Haas effect as a psychoacoustical effect. When a sound is followed by another sound separated by a sufficiently short time delay (below the listener’s echo threshold), listeners perceive a single auditory event. Its perceived spatial location is dominated by the location of the first-arriving sound (the first wavefront). The lagging sound also affects the perceived location. However, the first-arriving sound suppresses its effect.
The Haas effect applies to many modern technology areas. Sound reinforcement systems, ambiance extraction, multichannel audio encoding and so on. Furthermore, here we will mention the appliance of the Haas effect in the music production. So, you can apply it to get a wide, open and spacious sound resulting in a more realistic sense of depth. In our example, we’ll use a stereo-delay plug-in to achieve this effect.
Try to remember
There are three things to remember:
1) Set the delay time on the side where you want to perceive the sound is coming from to ‘0’ (no delay)
2) Set the delay time on the opposite side anywhere from 1 ms – 35 ms. Solo your track and increase the delay time starting from ‘0’ and listen!
3) Watch for a possible loudness increase since you are converting your mono track into a stereo track when you insert the stereo delay plug-in. Therefore, my suggestion would be to set the ‘MIX’ control on both sides of the stereo-delay to 50%. Adjust your track volume accordingly.
Additional resources & source texts