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8.3 Early Reflections
Another situation that can reduce the subjective quality of reproduced sound is the presence of
early reflections. By early reflections, we are referring to reflected sound waves that reach the
listener within 10 to 20 milliseconds of the direct signal from the loudspeaker.
When a reflected sound reaches the listener more than 40 milliseconds later than the direct
sound, the reflection is heard as a discrete echo. However, if the reflected sound arrives within
around 20 milliseconds of the direct sound, the ear/brain system integrates the two sounds so
that only one sound is heard. This integration is done in such a way that spatial information is
preserved, providing an acoustical "picture" of the physical space that created the reflections.
However, the source recording also contains ambient information that portrays the original
recording site. Early reflections in the listening room will tend to obscure the ambient
information in the recording, leading to a loss of dimensionality or spaciousness. Secondary
arrivals within the first 10 milliseconds are especially problematic, becoming less
troublesome as the arrival time lengthens to 20 milliseconds or so.