Direct sound weakens by a factor of four for every doubling of distance

Evidence

For speech it is important that the listener receive a large amount of direct sound if they are to comprehend the words easily. Unfortunately, as discussed in Chapter 1, the direct sound gets weaker as it spreads out from the source. Every time you double your distance from a sound source the level of the direct sound goes down by a factor of four, that is, an inverse square law. Thus the further away you are from a sound source, the weaker the direct sound component. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2434

Categorization

• DEFINE: States the inverse square law in its operational form: double the distance, quarter the level.
• XREF: Directly extends the Chapter 1 inverse-square material and feeds the direct-to-reverberant ratio used later in this chapter.