I think that calling it a "pinger" is a bit misleading.
It's a towed listening device - the sonar pings are produced by the main vessel
The reason it's towed is to keep it some kilometers from the ship noise so it has a wider area to listen to
innaflap,
Your reply is even more misleading!
The ADV Ocean Shield is NOT putting out any pings. The towed pinger locator is purely a passive device, listening for the 37.5 kHz ultrasound signal from the CVR and FDR pingers.
The reason the cable is very long (several thousand metres) is that it is the only way you can "fly" the towed pinger locator at its operational depth, when the Ocean Shield is moving at two or three knots. It is NOT to do with ship noise. The length of the cable is also the reason that turn arounds take so long. I read somewhere that much of the cable is reeled in before turning and then let out again.