OVERVIEW: Acoustic decoys are countermeasure devices designed to disrupt or divert passive and active sonar detection. By producing acoustic noise and obscuring sonar returns, they reduce the likelihood of submarines or surface ships being accurately located or targeted.

DETAILS: These decoys function by releasing a stream of gas bubbles or deploying small explosive charges in the water to create a dense acoustic environment. The bubble screen reflects, scatters, and absorbs sonar pulses, degrading the effectiveness of enemy sonar systems. In some configurations, these noisemakers are towed behind submarines or launched as expendable devices to simulate vessel signatures. They are particularly effective in masking maneuvers or enabling evasive actions when under sonar tracking.

ROLE SUMMARY:
Category: Naval Countermeasure
Primary Use: Sonar disruption and deception
Function: Acoustic interference through bubble generation and noisemaking
Strong Against: Passive and active sonar systems, acoustic torpedoes, submarine detection
Weak Against: Wake-homing torpedoes, non-acoustic tracking systems, close-range detection
Platform: Submarines and surface combatants
Integration: Compatible with countermeasure launchers, towed decoy systems, and expendable pods

SOURCE:
Janes Naval Weapon Systems
https://en.wikipedia.org/wiki/Acoustic_decoy