Pinging, explosions, screw sounds during TC

[gumbeau]

I just got SH4. First try at a war patrol. While in Time Compression I hear pings, explosions and sounds of a ship screw passing in doppler.

Why?

and how do I turn it off?

[1480]

There is an option in the sound options menu, I can't remember the exact name for it (realistic sound/TC or something like it) and uncheck it.