Acoustic torpedoes (sometimes, sonar torpedoes) are an utility ammunition, well known ever since World War II. The charge carried by this torpedo creates a powerful sound wave upon explosion, temporarily making sonars useless. Additionally, the ping from this sound wave can be used by the passive sonar to trace the objects located close to the acoustic torpedo's explosion.
Also, if the enemy vessel has a human sonar operator, an explosion of an acoustic torpedo will likely deafen that person, which makes them especially dangerous against submarines with human crews (I-401, U-2501 as well as Hakugei III).
The charge in the acoustic torpedo's warhead lacks the power to do any noticeable damage to a vessel's armor, but it is still powerful enough to detonate other torpedoes and anti-submarine missiles nearby, which means that the acoustic torpedoes can be used as the last desperate attempt to protect the vessel from incoming barrage.
Most commonly, acoustic torpedoes can be found on various submarines, however, surface vessels may have these torpedoes in their arsenals as well. Heavy cruiser Ashigara used acoustic torpedoes during her searches for I-401 by detonating them and listening to 'pings'.
- Acoustic torpedoes are the second most often used torpedoes in "Aoki Hagane no Arpeggio". Only Corrosive Warhead Torpedoes are used more often.
- Sound-Cluster torpedoes used by Hakugei III in a way are the spiritual successors of Acoustic torpedoes. However, unlike Acoustic torpedoes, which explodes for a single but very powerful sound wave, a Sound-Cluster torpedo creates a continuous curtain of sound to hide a submarine from enemy sonar.