My grandfather (chief machinist on board the submarine torricelli in june 40, red sea, war cross for gallantry in action, he was wounded too and passed 7 years in pow camps in india, after scuttled the boat.) was ambushes by an hunter killer group in june 40 in perim strait, after a couple of days of cat and mouse game, they was forced to gun action. Badly damaged the hms sorehan and the hms karthoum (the last sunked the day after for unclear reasons maybe for the damages. A shell from the italian sub hit her torpedo depot.) and later being hit scuttled the boat for avoid capture.
He told me that the noise he heard (they stilled 12-18 hours on the sea floor, damages, and chased, witg 45-50 degrees inside, in shadow.) during the hunt, was something like if someone was beating the hull, but a very light noise, not like a hammer, and later something like "pstchhhh".for a couple of secobds the beating, and so something like a "pstchhh" .
Also the italian escort sonar should have been similar. Because in alfa tau (a movie about the duel between hms triad and the submarine enrico toti) is very similar.
So he understood they was pinged.
The skipper passing in engine room, saw him was smiling, and asked: are you mad? But my old (18 years old, the most young of the crew) answered: no sorry captain, only is ironic that today it s my birthday and the enemy is bombing us.
Btw i guess there was diverse types of sonars. Some like if you throw sand on the hull, or an hammer noise, others like what we see in game. But someone sad me,(source: navyman) that when they launch 1 only ping, the sound was "piing" like we know, when they was contibuosly pinging, it seems that sand was throw against the hull. All could be guys.