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.