False contacts while on the surface?

[panthercules]

Been wondering a little about this myself lately - running 1.3 with heavily modded RFB1.31 with NSM and ROW.

I'm pounding along surfaced at flank speed in light seas (5m/s) in mid-December 1941 in my Salmon class boat off the Luzon Straits, trying to chase down a Japanese task force in which I severely damaged a Mogami class cruiser before being forced down by the numerous destroyers. They've got a pretty good head start on me, and there are no visible contacts (good daylight visibility, so out to maybe 7-8 nm). Now I start getting sound contacts being called out. I know there were some sound heads below water-line, and I would anticipate being able to maybe hear something while surfaced at dead slow or all-stop, but at flank speed??? I haven't had time to do any real research, but something just "feels wrong" about this. I would have thought that the noise of our own engines and the water rushing by the hull, etc. would have made it virtually impossible to detect any meaningful sound signals while surfaced at flank speed.

Eventually I guess the radar will make this a non-issue, but in these early war, pre-radar patrols it seems kind of weird to be getting these contacts. Is there any way to tone this down based on your own boat's speed or else just disable the hydrophones from working on the surface? I thought I saw something about how to do this back when folks were trying to get the 'phones to work at periscope depth early on, but I haven't been able to locate those old threads yet.