OVERVIEW: The torpedo decoy is a naval defensive countermeasure designed to protect surface vessels by distracting and confusing incoming torpedoes through acoustic and electronic signature deception.

DETAILS: Deployed from ships, this expendable device emits simulated acoustic signals that mimic a ship’s noise and movement, drawing torpedoes away from their true target. The decoy can generate broadband or frequency-specific noise patterns and is often equipped with propulsion or drifting capabilities to enhance realism. Its activation is typically automatic upon torpedo detection, providing critical time for evasive maneuvers or counterattacks. The system is effective against both passive and active homing torpedoes, reducing the risk of successful strikes.

ROLE SUMMARY:
Category: Naval Torpedo Defensive Countermeasure
Primary Use: Distraction and confusion of incoming torpedoes
Function: Emission of acoustic and electronic signatures to mislead torpedo seekers
Strong Against: Passive and active acoustic homing torpedoes
Weak Against: Advanced torpedoes with multi-sensor guidance and sophisticated counter-countermeasures
Platform: Surface combatants equipped with decoy launching systems
Integration: Integrated with ship’s sonar and defense systems

SOURCE:
Janes Naval Electronic Warfare Systems
https://en.wikipedia.org/wiki/Torpedo_decoy