OVERVIEW: Acoustic intercept systems are passive underwater sensors designed to detect, classify, and track acoustic emissions from naval platforms or incoming threats such as torpedoes. These systems are critical to submarine situational awareness and self-defense.

GENERAL DESCRIPTION: Acoustic intercept systems function by monitoring ambient underwater sound and identifying sudden or structured acoustic events, such as active sonar pings, propulsion noise, or torpedo launch signatures. Unlike active sonar, they operate passively and provide bearing-only data, maintaining stealth for the host vessel. Installed on submarines and surface ships, they are capable of alerting crews to threats such as approaching torpedoes or nearby sonar activity. Systems often include signal classification algorithms and directional hydrophone arrays to isolate bearing angles. Intercept systems can trigger automatic evasive maneuvers or cue countermeasure deployment.

ROLE SUMMARY:
Category: Passive Acoustic Surveillance / Torpedo Warning
Primary Use: Detection and classification of hostile sonar and underwater threats
Function: Real-time acoustic monitoring and threat alerting
Platform: Submarines, surface combatants, some unmanned underwater vehicles (UUVs)
Export: Common among NATO, Russian, and Asian naval platforms
Integration: Works with sonar suites, combat systems, and countermeasure launchers

Type: Passive acoustic detection system
Processing: Directional signal processing and threat classification
Sensor Type: Hull-mounted or conformal hydrophone array

See Specific information under [Sensors/EW] section.

SOURCE:
SIPRI Naval Electronics Database
https://en.wikipedia.org/wiki/Sonar#Acoustic_intercept_systems