Torpedo sound levels and enemy detection

[Capt Jack Harkness]

It's now a commonly known bug that enemies can hear torpedoes being activated, even in their baffles, and I may have found an explanation.

Looking in weapons.txt I found that the Mk 16 emits 140 dB at all times, makes sense. The Mk 37 starts at 120 dB, also makes sense, but then jumps to a whopping 230 dB as soon as it's enabled! No wonder anyone anywhere can hear it activate. The Mk 48 similarly starts at 160 dB and jumps to 230 dB when enabled.

So I decided to look at some values that make more sense for the 37, then move to the 48. With the Mk 37 we have a 17 kt run speed and 26 kt enable speed, that's roughly a 50% increase in speed so about a 100% increase in motor power, right? So that means the sound energy from the motor doubles plus the difference in flow noise. Since sound energy increases by a factor of 2 for every 3 dB it looks like the Mk 37 enable noise should only be 123 dB. And if we use the sonar self noise factor of 1 dB loss for every knot of speed to roughly anticipate flow noise that gives us 9 dB, or 132 dB total.

Does any of that math make sense to you guys or have I been doing this all wrong?

[The Bandit]

Originally Posted by Capt Jack Harkness

It's now a commonly known bug that enemies can hear torpedoes being activated, even in their baffles, and I may have found an explanation.

Looking in weapons.txt I found that the Mk 16 emits 140 dB at all times, makes sense. The Mk 37 starts at 120 dB, also makes sense, but then jumps to a whopping 230 dB as soon as it's enabled! No wonder anyone anywhere can hear it activate. The Mk 48 similarly starts at 160 dB and jumps to 230 dB when enabled.

So I decided to look at some values that make more sense for the 37, then move to the 48. With the Mk 37 we have a 17 kt run speed and 26 kt enable speed, that's roughly a 50% increase in speed so about a 100% increase in motor power, right? So that means the sound energy from the motor doubles plus the difference in flow noise. Since sound energy increases by a factor of 2 for every 3 dB it looks like the Mk 37 enable noise should only be 123 dB. And if we use the sonar self noise factor of 1 dB loss for every knot of speed to roughly anticipate flow noise that gives us 9 dB, or 132 dB total.

Does any of that math make sense to you guys or have I been doing this all wrong?

This is really interesting, but I think some tests will have to be done here. The Mk 37 was noted to be a fairly quiet torpedo and it seems that the Mk 48 was at least quiet, or not notably louder (most likely thanks to the pump-jet) according to what I've read.

I think taking some steps to "correct" its self-noise at full speed may gain a bit more flexibility for the Mk 37, but I can't help but wonder, if the level is lowered so that they can no longer hear it in the baffles, what is that going to do to the non-baffle detection range. I guess what I'm trying to say here is that some care has to be taken not to make the torpedoes TOO stealthy.

[Kazuaki Shimazaki II]

Originally Posted by Capt Jack Harkness

Looking in weapons.txt I found that the Mk 16 emits 140 dB at all times, makes sense. The Mk 37 starts at 120 dB, also makes sense, but then jumps to a whopping 230 dB as soon as it's enabled! No wonder anyone anywhere can hear it activate. The Mk 48 similarly starts at 160 dB and jumps to 230 dB when enabled.

The only reason Mark 16 doesn't leap, I think, is that it is straight running and it isn't going to work if the enemy can hear and dodge it. The whole "whopping" leap is probably a game feature that both simulates the active regime plus ensures both sides get SOME warning of torpedoes. It might not be very realistic, but it is kind of fair.

[Capt Jack Harkness]

Isn't noise from active sonar handled elsewhere in the files? This makes passive torpedoes no more stealthy than active ones.

[Capt Jack Harkness]

So I've been playing around with this more using a barely educated guess to set noise levels on all the torpedoes in the game.

With a 120 run speed and 130 enable speed on a Mk 37 enemy subs will still hear if a torpedo goes active and they will hear a passive torpedo with enough distance to go evasive with moderate success. They now seem to be oblivious to torpedoes enabling in passive in their baffles but that needs more testing.

Surface ships seem to pick up a Mk 37 in either mode, enabled or not, with plenty of time to evade.

Hostile torpedoes are more difficult to track before they enable but not by enough to matter.

Haven't messed with the MOSS yet, it runs at 230 dB all the time. I might set it to the Skipjack's 140 dB and see what happens. Technically the MOSS noise level should be the same as the launching boat but that would add a whole layer of needless complication if it could be achieved at all.

[kondor999]

I know this thread is ancient, but I feel like the loudness of the Mk 48, even before it's activated (160db!) is essentially a game-breaking giant bug.

It ensures that you can only very rarely do a true dog-leg sneak attack, because the enemy sub will nearly always hear the incredibly loud torp and do an immediate counter-launch down its bearing.

This is why Cold Waters is so inferior to Red Storm Rising, where such sneak attacks were the core gameplay element. In Cold Waters, instead of careful surprise attacks, everything quickly degenerates into a swirling underwater "dogfight" with torps everywhere.

By lowering the noise of the Mk48 down to a more reasonable 120 or 130db (prior to going active) and 180db (full speed - because I really doubt a torp is louder than a MOSS decoy at 200db), suddenly you get the sub game we all wanted.

Now you can launch a Mk48 in passive mode, guide it carefully into attack position via a dog-leg, make it go active and watch as the enemy fires a spread vs the incoming torp - but away from your subs actual position.

This is vastly more interesting and (I feel) more realistic than watching a November somehow magically know exactly when I've fired a Mk 48 at extreme range in passive mode (which is how the game plays as-is).

I've gone through and adjusted all the torp loudness values, making the electric ones quite quiet and the Otto-cycle ones louder - but never louder than an *entire mid-80's nuclear sub* prior to activation.

The result is a much better game for sure, and likely a much better simulation was well. Kudos to Killerfish for making all these files edit-able, but they lose points for rating the Mk48 at 160db/230db to begin with, which (as I've said) pretty much kills the game for me.

[Treetop64]

Originally Posted by kondor999

I know this thread is ancient, but I feel like the loudness of the Mk 48, even before it's activated (160db!) is essentially a game-breaking giant bug.

It ensures that you can only very rarely do a true dog-leg sneak attack, because the enemy sub will nearly always hear the incredibly loud torp and do an immediate counter-launch down its bearing.

This is why Cold Waters is so inferior to Red Storm Rising, where such sneak attacks were the core gameplay element. In Cold Waters, instead of careful surprise attacks, everything quickly degenerates into a swirling underwater "dogfight" with torps everywhere.

By lowering the noise of the Mk48 down to a more reasonable 120 or 130db (prior to going active) and 180db (full speed - because I really doubt a torp is louder than a MOSS decoy at 200db), suddenly you get the sub game we all wanted.

Now you can launch a Mk48 in passive mode, guide it carefully into attack position via a dog-leg, make it go active and watch as the enemy fires a spread vs the incoming torp - but away from your subs actual position.

This is vastly more interesting and (I feel) more realistic than watching a November somehow magically know exactly when I've fired a Mk 48 at extreme range in passive mode (which is how the game plays as-is).

I've gone through and adjusted all the torp loudness values, making the electric ones quite quiet and the Otto-cycle ones louder - but never louder than an *entire mid-80's nuclear sub* prior to activation.

The result is a much better game for sure, and likely a much better simulation was well. Kudos to Killerfish for making all these files edit-able, but they lose points for rating the Mk48 at 160db/230db to begin with, which (as I've said) pretty much kills the game for me.

It's not unreasonable for the Mk48 to be as loud as they are represented in-game.

IRL Mk48s and the later ADCAPS are in fact exceptionally noisy torpedoes. This is a notable drawback and chief characteristic of the type. An effect of their corresponding high performance.

IIRC, it wasn't until the ADCAP Mod-6 (a late modification that wasn't deployed until after the SSN-21s were already in service) that the ADCAP's noise levels were thoroughly addressed without impeding performance. The result was an even higher performance torpedo with better sensors that ran quieter than legacy models, though relatively it still runs loudly for a modern torpedo.

[shipkiller1]

Are you all talking about radiated weapon noise pre-enable or post-enable? It make a difference.

[Treetop64]

Of course it makes a difference.

I'm talking about in general.

[shipkiller1]

Standard heavyweight torpedo's are not stealth weapons. They all radiate a lot of broadband noise due to their design. High speed coupled with small propulsion mechanics makes this assured. It is just basic physics.

Anytime a weapon gets to the enable point and goes active, there is NO stealth evolved. You are radiating a high power sonic pulse to get an adequate return for the weapon to perform.

Most modern submarine forces have some type of dedicated active intercept receiver, or modes of operation tuned to the expected weapon frequencies of adversary. Anything less is just stupid....

So yes, when the weapon lights off, he's going to hear it....even if he is outside of the weapons range. I find the Russians expected alertment range against a MK-48 (pre-enable or post-enable) reasonable.

The surface ships on the other hand is highly exaggerated. Especially when running over 20kts.

[Treetop64]

Originally Posted by shipkiller1

Standard heavyweight torpedo's are not stealth weapons. They all radiate a lot of broadband noise due to their design. High speed coupled with small propulsion mechanics makes this assured. It is just basic physics.

Anytime a weapon gets to the enable point and goes active, there is NO stealth evolved. You are radiating a high power sonic pulse to get an adequate return for the weapon to perform.

Most modern submarine forces have some type of dedicated active intercept receiver, or modes of operation tuned to the expected weapon frequencies of adversary. Anything less is just stupid....

So yes, when the weapon lights off, he's going to hear it....even if he is outside of the weapons range. I find the Russians expected alertment range against a MK-48 (pre-enable or post-enable) reasonable.

The surface ships on the other hand is highly exaggerated. Especially when running over 20kts.

Noooo.

Really?