To use sound analysis, the character must work in conditions of
absolute silence. The sound he creates must have a sharp,
somewhat staccato quality. A howl or wail is ineffective, but a
clicking sound or loud “hey” works well.

When this proficiency is used, the player must make a Proficiency Check. If the check is successful, the character has correctly
analyzed the size of the area in question, within the
following margin of error:

Length: + or -30%
Width: + or -25%
Height: + or - 25%

If the check fails, the echo has become garbled in the course of
its reverberations. No further attempts to analyze the same area
by that character will be successful. Other proficient characters
may still try their luck, however.

A Proficiency Check of 5 or less means that the character has
learned not only the size of the analyzed area, but additional
details about it as well. The DM should tell the player which
aspects of an area it is possible to learn about in this way. Examples
include the number of side passages branching off the analyzed
area, a sense of whether the area runs straight or winds
around considerably, or even if the area contains a body of water.

An obvious disadvantage of this ability is that while it is most
useful for learning about an area totally new to the PCs, using it
announces the presence of the party. Creatures hearing sound
analysis used will certainly be prepared for some kind of intrusion
and might even go looking for the perpetrators. This proficiency
can be used in conjunction with the animal noise proficiency.