An acoustic torpedo in flight
Acoustic Torpedoes are a special type of torpedo, intended not to destroy enemy ships but rather to assist in the location of objects hidden in dense clouds.
Acoustic Torpedoes are designed to create as loud of a noise as possible when they detonate. The ship's acoustic officer can then listen for the echo, allowing them to locate and identify objects in the Grand Stream which can't be easily seen through the clouds.
Alex Row had acoustic torpedoes specially manufactured by Walker and loaded onto the Silvana and the Urbanus as part of the plan to capture Exile.