A '''towed array sonar''' is a system of hydrophones[[hydrophone]]s towed behind a [[submarine]] or a surface ship on a cable.<ref>{{cite news|url=http://www.eie.polyu.edu.hk/~enktwong/ktw/TichavskySPT0104.pdf|title=Quasi-Fluid-Mechanics-Based Quasi-Bayesian Cramér–Rao Bounds for Deformed Towed-Array Direction Finding|author=Petr Tichavský and Kainam Thomas Wong|work=IEEE TRANSACTIONS ON SIGNAL PROCESSING|volume=52|edition=1|date=January 2004|page=36}}</ref> Trailing the hydrophones behind the vessel, on a cable that can be kilometers long, keeps the array's sensors away from own-ship's-noise sources, greatly improving its [[signal-to-noise ratio]], and hence the effectiveness of detecting and tracking faint contacts, such as a quiet, low noise-emitting submarine threats, or seismic signals.<ref name="Defence Today">{{cite news|url=http://www.ausairpower.net/SP/DT-TAS-Dec-2009.pdf|title=Identification underwaterwith towed array sonar|author=Carlo Kopp|work=Defence Today|date=December 2009|pages=32–33}}</ref>
A towed array offers superior resolution and range compared with hull mounted sonar. It also covers the [[Baffles (submarine)|baffles]], the blind spot of hull mounted sonar. However, effective use of the system limits a vessel's speed and care must be taken to protect the cable from damage.
