Distance changes level, but the room changes the rule.
Estimate the idealized level change between two distances while keeping real-world reflections, barriers and source behavior in view.
Spherical spreading
An ideal point source in a free field loses about 6 dB each time distance doubles. The calculation uses the ratio between the two entered distances.
Real places are not free fields
Walls, floors, terrain, barriers and source directivity alter propagation. A line source can follow a different distance relationship.
Use the result as a comparison
The FHWA measurement handbook describes the free-field point-source assumption and its limits.