Cannot tell you for sure one way or the other mate.
All I can give you is some sketchy "well this happened to me" stories
Whilst broadside to an enemy sub I have launched, and despite the fact that their sonar fix on me was very poor (well into the minus tens or twenties), they seemed to react straight away and counter launch and go active
However, I have launched on enemy subs when I am deep in their baffles (-50 on both their sonar figures)
In these cases I have seen them not react until my torps are within a few thousand yards
Just some anecdotal evidence
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