even in stock 1.4, the escorts are not deaf/dumb.
To increase your chances of not being detected, the best course of action is to dip below the thermal layer & go to silent running.
"silent running" basically gives you a stealth bonus and reduces the passive sonar range of enemy escorts. You can see it visually in SH5 w. map updates "on". From my experience, it appears to work the same way in SH4.
Although in RFB, which is what I use, you can still be detected if the escort is close enough.
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