Marco,

The performance of WW2 passive sonars (at least allied surface and submarine sonars) was very poor.The sonars tended to be small (hence opperateing at high frequency to maximise gain) and had poor range.You must also remember that passive sonars mounted on allied escorts had HUGE self noise issues.The escorts were small warships with no acoustic insulation and propellors which cavitated at all speeds above a few knots.The escots own noise would drown out
most submarine noise...especially if the sub was deep and running silent.

German passive sonars based on the GHG array technology had the best performance of passive sonars.By the end of the war the GHG mounted on the type XXI had a range of approx 100 miles against a convoy and around 10-15 miles against a single ship.When you compare this with the average range of an allied surface ship passive sonar of approx 3000-4000 yards (under optmal conditions) you can see the advantage the Germans enjoyed over the allies.

As an aside....when the allies captured the cruiser 'Prinz Eugen' at the end of the war they were very interested in her passive sonar.It was based on GHG technology (it was an group of hydrophones wired together to produce an array which could be 'steered' electronically).This passive sonar was HUGE, nearly 30 feet in diameter and had amazing performance for a 1940's peice of equipment.This sonar in service once detected a British heavy crusier at 30,000 yards range while the 'Prinz Eugen' was steaming at her top speed of 30 knots.This sort of performance is remarkable even today,but in the 40's was littlw short of remarkable.

Sniper.