View Full Version : Calc Speed Using Hydrophone?

03-24-2007, 03:07 AM
Just wondering how to calculate speed using the hydrophone by counting RPMs? i know theres a tutorial for it somewhere, i just cant find it. need to learn how to calculate speed for SH4 since the darn clock is broken.

Thanx in Advance.

03-24-2007, 07:07 AM
This is it.


Here is a link to sound trainer tutorial: http://www.subsim.com/subsim_files/patches05/sound_trainer.zip

Note: It was designed for Stock game!

Here is my mod:


I don`t know where I posted it for download.
So if you want it badly PM me your e-mail.

03-24-2007, 07:27 AM
Messervy, can you please explain how exactly one counts the RPM's?? On the hydrophone, all I can hear is the thumping of a ship's engine. That does not exactly help, because I can't figure out the ratio between the thumps and RPM's..... Care to explain please??

03-24-2007, 10:20 AM
There is a link beetwen the two pictures I have posted if you would like to check out. http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

For those too lazy I made an effort:

Speed of the target
As soon as possible, decide the probable kind of target. If it is a ship, notice the speed of
the screws (slow, medium, or fast) and the weight of the sound (light or heavy).
Determining the targets speed will help in identification through elimination. See tables.
Train the hydrophone directly on the bearing where the prop beats are loudest.
Notice whether the beats are accented or unaccented. Accented beats go CHUG, chug,
chug (three-bladed propeller)-or CHUG, chug, chug, chug (four-bladed propeller).
Unaccented beats go chug, chug, chug, chug, chug.
Get in rhythm with the beats by pumping your arm up and down like a band conductor. If
there is an accented beat, let your hand come down with every accented CHUG -or if the
beats are all the same, on every chug.
Count the number of times you pump your hand down in 15 seconds.
Multiply this count by 4 to get the number of rpm (revolutions per minute). For example,
if your 15-second count is 12, the rpm will be 48. If the beats are too rapid count for a full
minute for accuracy.
For the merchants, the screws have a cycle of four beats, of which you only count the
first beat, or begining beat. To me the cycle sounds like the beating of the war drums of
the cheyanne, or apache. Another analogy is music in four four time, four quarter notes,
four beats to a measure, 1- 2-3-4 1-2-3-4, count the beats of the 1 only.

03-24-2007, 10:33 AM
Thanks a lot!! http://forums.ubi.com/images/smilies/inlove.gif I didn't notice the link for some odd reason

03-24-2007, 11:38 AM
Messervy, it doesn't work. I followed those instructions to the letter. Now, in the sound trainer, the speed of a merchant is 5 knots according to the old-fashioned waay of measuring speed. THis is a C2, by the way. It has a 3-bladed propeller, so the thumps go THUMP-thump-thump-THUMP-thump-thump... I counted the accented THUMP for 15 seconds, multiplied by 4 and got about 60RPM... Which doesn't seem possible, according to the charts. What am I missing?

03-25-2007, 06:07 AM
Ahh yes, thanx! was looking for that tutorial. Anyways, since SH4 provides new boats, how to find out what speed match with what RPMS other than setting up a mission with the mission editor, or just trial and error? [in the config files or ship files?]

03-25-2007, 06:50 AM
@ Foehammer

Are you useing any mods?
Try 1/4 - I don`t remmember counting every third thump and it worked for me.

03-25-2007, 10:00 AM
If two or more ships are (approx) in the same line you'll get garbled sound, and 'harmonic' THUMPS that will make you think the ship is at warp speed or not moving that fast.

I had this once when I got a single ship report and monitored the hydrophone for an hour or so. I just could not 'nail' the revs. I came in at an angle that the smaller ship was totally concealed by the larger one, visually and audibly (dark and rainy/misty night). I got in close enough to get 2 hits on the big one. My surprise when I heard the 2nd ship revv up and get away http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

03-25-2007, 03:35 PM
It's weird how a C2 sounds sometimes. A small merchant sounds THUMP thump thump... The C2 sounds something like THUMP-thump-thump; THUM-THUM-thump-thump;Thump-thump-thump; THUM-THUM-thump-thump..... so how do I count those I wonder?? http://forums.ubi.com/groupee_common/emoticons/icon_confused.gif