Sound from a source falls 6 dB per distance doubling until reverberation takes over

Evidence

The direct sound pressure level decreases by 6 dB for every doubling of the distance. At a certain distance, called the reverberation distance or the radius of reverberation, the direct and reverberant fields have the same level, and this is Figure 2. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 286

Categorization

• DEFINE: Defines the reverberation distance — the crossover point where direct and reverberant fields are equal, a key room-acoustics concept.
• ADDENDUM: Directly relevant to how builders/sound designers control distance perception indoors — connects to the spatial-sound applications thread.
• corroborated: 2 independent passages support this claim — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 286