Digital Sound & Music: Concepts, Applications, & Science, Chapter 4, last updated 6/25/2013
Figure 4.34 Resonant frequency on a flat plate
18.104.22.168 The Precedence Effect
When two or more similar sound waves interact in the air, not only does the perceived frequency
response change, but your perception of the location of the sound source can change as well.
This phenomenon is called the precedence effect. The precedence effect occurs when two
similar sound sources arrive at a listener at different times from different directions, causing the
listener to perceive both sounds as if they were coming from the direction of the sound that
The precedence effect is sometimes intentionally created within a sound
space. For example, it might be used to reinforce the live sound of a singer on
stage without making it sound as if some of the singer’s voice is coming from a
loudspeaker. However, there are conditions that must be in place for the
precedence effect to occur. First is that the difference in time arrival at the
listener between the two sound sources needs to be more than one millisecond.
Also, depending on the type of sound, the difference in time needs to be less
than 20 to 30 milliseconds or the listener perceives an audible echo. Short
transient sounds starts to echo around 20 milliseconds, but longer sustained sounds don't start to
echo until around 30 milliseconds. The required condition is that the two sounds cannot be more
than 10 dB different in level. If the second arrival is more than 10 dB louder than the first, even
if the timing is right, the listener begins to perceive the two sounds to be coming from the
direction of the louder sound.