Reflection path length can be computed geometrically using the image-source method.

Evidence

A loudspeaker radiates a peak sound intensity of 102 dB at 1 m. What is the sound intensity level (Ireflection) and delay relative to the direct sound of an early reflection when the speaker is 1.5 m away from a hard reflecting wall and the listener is at a distance of 4 m in front of the loudspeaker? The geometry of this arrangement is shown in Figure 6.5, and we can calculate the extra path length due to the reflection by considering the “image” of the loudspeaker, also shown in Figure 6.6, and by using Pythagoras’ theorem. This gives the path length as 5 m. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1704

Categorization

• XREF: The image-source technique connects to broader room-acoustics methods for predicting early reflections.