Ghost sound allows the character to create a volume of sound
that rises, recedes, approaches, or remains at a fixed place. The
character chooses what type of sound the spell creates when
casting the spell and cannot thereafter change its basic
character. The volume of sound created, however, depends on the
character's level. The character can produce as much noise as
four normal humans per caster level (maximum twenty humans).
Thus, talking, singing, shouting, walking, marching, or running
sounds can be created. The noise a ghost sound spell produces can
be virtually any type of sound within the volume limit. A horde
of rats running and squeaking is about the same volume as eight
humans running and shouting. A roaring lion is equal to the noise
from sixteen humans, while a roaring dire cat is equal to the
noise from twenty humans.
Note that ghost sound can enhance the effectiveness of a
silent image spell.