For Questions That Don't Merit Their Own Thread

[magnemoe]

4 hours ago, JoeSchmuckatelli said:

Any audiologists or sound engineers here?

Would adding a Bose-like 'noise canceling speaker' to a computer case (something that would detect the noise of the computer and all its fans and put out the reverse frequenc(y/ies) work to reduce the impact of the constant white noise fan whine? 

It might but it would be sensitive to direction. One idea for fan and coolers with in build fans like on graphic cards would be to add speakers to the fans to cancel their noise. 
Note that if air flow is high the moving air also create noise. 

I have my sound dampened  computer case inside an cabinet on my desk, it has an funnel on top who direct the air blowing from the top out at the back, yes you can hear it if no other stuff making noise but quite. 
And its an gaming pc. 

[JoeSchmuckatelli]

11 minutes ago, magnemoe said:

sound dampened  computer case

Googling that now

 

[Beamer]

36 minutes ago, JoeSchmuckatelli said:

Googling that now

 

I've been using quiet computer cases for a long time (I have a 24/7 server running in the same room where I sleep), they really make a huge difference. Don't go too cheap though, quality really matters in this case - no pun intended. A cheap "silent" box will just be a normal box with some foam padding on the inside panels which really doesn't make much of a difference if the rest of the case hasn't been designed with sound dampening in mind. You'll want something heavy so it doesn't vibrate (thicker steel than the usual box, weight is a telling indicator for quiet computer cases) and with some well thought out airflow channels.

I've used quiet cases from Corsair and CoolerMaster in the past and currently have a "BeQuiet! Pure Base 600", these were all in the 60-100 euro range IIRC (full tower size) and they all were quite good. So it doesn't have to be super expensive but if you see a case advertised as quiet and it's only 20-50 euro, be wary (especially if that price includes a PSU, in which case they didn't even use actual sound dampening foam but probably just grabbed some spare packaging material they had lying around and glued it to the inside of the case).

Also pay attention to what you put in it of course, many brand PSUs come in a quiet version for just a few euros more which helps a lot since those are blowing their noise right out of the case. You'll also want low RPM case fans of course (often come included with the brand cases), and a quiet aircooler or watercooling for the CPU. If your computer is often on while you're not using it, run your OS and resident apps from a SSD so your spinning disks (if you still use those) can go to sleep mode.

 

[TheSaint]

15 hours ago, JoeSchmuckatelli said:

Any audiologists or sound engineers here?

Would adding a Bose-like 'noise canceling speaker' to a computer case (something that would detect the noise of the computer and all its fans and put out the reverse frequenc(y/ies) work to reduce the impact of the constant white noise fan whine? 

Noctua fans. My computer sits directly next to my seat in the living room, so I'm kinda sensitive to how much noise it makes. The last time I did an upgrade on it, I kept the old cheap case, but I got rid of all of the old cheap fans and replaced them all with Noctua fans (and a Noctua CPU cooler). World of difference. Now the problem I have is that if the monitor goes into power save I have to look at the lights on the front of the computer to see if it's running. It's that quiet. 

Edited November 3, 2022 by TheSaint

[mikegarrison]

14 hours ago, JoeSchmuckatelli said:

Any audiologists or sound engineers here?

Would adding a Bose-like 'noise canceling speaker' to a computer case (something that would detect the noise of the computer and all its fans and put out the reverse frequenc(y/ies) work to reduce the impact of the constant white noise fan whine? 

Active noise control certainly could work, but there are most likely cheaper ways to do the same thing.

Other options: quieter bearings (which are more expensive), quieter fan blades, lower air velocities (which can be achieved with bigger fans and/or more efficient heat exchangers), mufflers on the air inlet and exhaust, and mass and/or damping on the computer case (depending on the frequencies you are trying to reduce -- mass works for low frequencies and damping works for high frequencies.

Active noise control works best to cancel out tones. It works worst to cancel out random noise like turbulence. If the problem is your fan blade tones, active noise control could be quite effective. If your problem is just turbulence from the airflow, more traditional mufflers would work better.

[DDE]

What is the correct English verb for travelling underwater under rocket propulsion?

[kerbiloid]

https://en.wikipedia.org/wiki/Cephalopod#Locomotion_and_buoyancy

Spoiler

 

[magnemoe]

2 hours ago, DDE said:

What is the correct English verb for travelling underwater under rocket propulsion?

Note that missiles launched  vertically from submarines do not ignite their rocket engines underwater but they uses compressed gas to launch them. Might be exceptions and I believe anti ship missiles launched from torpedo tubes do. However they have an special engine for this and drop it an activate an jet engine or other rocket engine after surfacing and is in stable flight. 
Makes sense as an rocket engine burning underwater is a bit special. 

[JoeSchmuckatelli]

3 hours ago, DDE said:

What is the correct English verb for travelling underwater under rocket propulsion?

Es gibt kein Wort 

(We would have to make one up - so I chose 'Shmurbeling'.  It combines the 'woosh' sound of a rocket with the cavitational 'burbling' sound I imagine a sub makes when going really fast. 

Thus from now and henceforth we shall describe the movement of rocket propelled subs as 'to shmurbel'. 

"The Royal Swiss submarine shmurbeled quickly through the heaving heart of the sea to escape the Malian flying dreadnought."

Oh - and as for missiles fired from the sub?  We simply say 'launched'. 

[DDE]

1 hour ago, magnemoe said:

Note that missiles launched  vertically from submarines do not ignite their rocket engines underwater but they uses compressed gas to launch them. Might be exceptions and I believe anti ship missiles launched from torpedo tubes do. However they have an special engine for this and drop it an activate an jet engine or other rocket engine after surfacing and is in stable flight. 
Makes sense as an rocket engine burning underwater is a bit special. 

Eh, I expected this retort. Makeyev's LRPE-based rockets of the R-29 line, like the one pictured above, kick in the vernier motor cluster while in the silo, and then ascend to the surface under 50% main engine power. We're talking about the same people who pickle the second stage engine inside the first stage's oxidizer tank; they're pretty special.

As you can see, there's little to no mortar assist, and with NTO being 50% denser than water and no space wasted on interstages, that thing isn't exactly buoyant:

So yeah, that's exactly why I've asked.

[mikegarrison]

4 hours ago, DDE said:

What is the correct English verb for travelling underwater under rocket propulsion?

Like, could that picture be any more phallic?

[DDE]

19 minutes ago, mikegarrison said:

Like, could that picture be any more phallic?

Come on, it's not a Blue Origin rocket.

[wumpus]

On 11/2/2022 at 8:38 AM, JoeSchmuckatelli said:

Any audiologists or sound engineers here?

Would adding a Bose-like 'noise canceling speaker' to a computer case (something that would detect the noise of the computer and all its fans and put out the reverse frequenc(y/ies) work to reduce the impact of the constant white noise fan whine? 

The straightforward answer is likely larger fans moving slower (same amount of air/time).  If they don't fit in the case, then you have to move to more complicated answers (like careful notches applied in the fans to reduce noise).  Pretty sure I'm not hearing any bearing noise in the fans, but they aren't spinning all that fast.  But I'd look for more quiet fans by starting with the largest that fit the case.  Not sure about sound dampening, but you should be able to get similar rubber sheets to add to side panels.  Granted, the only time I've ever seen them was in postal sorting machinery.  We ripped them out (they tended to collapse and interfere with the machinery) and cursed german engineering for making things to complicated and fragile.  Mufflers sound like an idea, but all air would  have to go in and out of separate mufflers, and they would obstruct the air so you'd need bigger fans.  I doubt they'd really work.

[TheSaint]

2 hours ago, magnemoe said:

Note that missiles launched  vertically from submarines do not ignite their rocket engines underwater but they uses compressed gas to launch them. Might be exceptions and I believe anti ship missiles launched from torpedo tubes do. However they have an special engine for this and drop it an activate an jet engine or other rocket engine after surfacing and is in stable flight. 
Makes sense as an rocket engine burning underwater is a bit special. 

Can't speak for Russian missiles. U.S. missiles operate as follows:

ICBMs are sealed in their tubes under a nitrogen purge. When they're launched, they have a small explosive charge which breaches the sealing cap at the top of the tube, and then they ignite a very small SRM at the base of the missile. The motor is not large enough to propel the missile, but is large enough to boil the seawater which is flooding the tube. This steam explosion forces the missile out of the tube, and it is propelled to the surface by what is essentially a steam rocket. It has a wet/dry sensor in its nose which tells it when it's breached, and then it ignites its first stage motor and goes.

Tomahawks are either VLS-launched or tube-launched. VLS-launched are propelled out of their canisters with a compressed gas charge, tube-launched are impulsed out of their canisters by seawater the same way a torpedo is impulsed out of the tube. Once it is clear of the canister, it ignites a small SRM that propels it up to the surface and clear of the water. Once it is clear it pops out the wings and air intake, starts its turbofan, and it's off to the races.

Harpoon was really interesting. The entire missile was encapsulated in a tube. The tube would be impulsed out of the torpedo tube and would float to the surface. Once the tip of the tube broached the surface, the cap at the end of the tube would pop off and the solid-rocket booster (which all Harpoons have) would boost it out of the tube straight up. When it was up to speed it would drop the booster, engage its jet engine, swoop over to its target heading, and off it went.

[kerbiloid]

3 hours ago, magnemoe said:

Note that missiles launched  vertically from submarines do not ignite their rocket engines underwater but they uses compressed gas to launch them.

The liquid fuel ones do. They use wet launch, when the shaft gets filled with water before the hatch opening, the pressure inside the shaft and fuel tank gets matching the water pressure outside, then the engine nozzle works like a hydrostatic bell for ignition and launch.

[mikegarrison]

35 minutes ago, wumpus said:

Mufflers sound like an idea, but all air would  have to go in and out of separate mufflers, and they would obstruct the air so you'd need bigger fans.  I doubt they'd really work.

Well-designed mufflers are highly effective. Poorly designed mufflers work poorly.

FWIW, I work in my company's "Noise, Vibrations, and Emissions" engineering group. Although I have done emissions for the past 20 years, for 12 years before that I was a noise control engineer. I have designed mufflers that are right now flying around on thousands of airplanes. I have seen people in our office rig up simple mufflers to reduce office noise sources just like this. After all, that kind of is our job....

Edited November 3, 2022 by mikegarrison

[wumpus]

1 minute ago, mikegarrison said:

Well-designed mufflers are highly effective. Poorly designed mufflers work poorly.

FWIW, although I have done emissions for the past 20 years, for 12 years before that I was a noise control engineer. I have seen people in our office rig up simple mufflers to reduce office noise sources just like this. After all, that kind of is our job....

So all you need to do is find some noise control engineers and convince them to do a custom job.  Curious if you could look up some speaker design information and simply design the worst speaker possible.  There might be more resources for that.

[darthgently]

On 11/2/2022 at 8:38 AM, JoeSchmuckatelli said:

Any audiologists or sound engineers here?

Would adding a Bose-like 'noise canceling speaker' to a computer case (something that would detect the noise of the computer and all its fans and put out the reverse frequenc(y/ies) work to reduce the impact of the constant white noise fan whine? 

Fans produce such broad spectrum noise that emanates from a such a broad area across the blades (that are spinning also) I think it would be hard to find a viable solution.

Enter liquid cooling with highly muffled or remote cooler for the liquid.

[steve9728]

The other extreme from quiet is the graphics card with a 'turbo' I have in my computer now, but unless I turn it on in the official software, it's generally pretty quiet. But... once I tried to pull the full speed... The sound made me wonder if there was an aero engine inside this computer.

[ARS]

If you mix oxidizer into flamethrower fuel, could you (in theory) use flametrower in space? How effective it's gonna be? I assume the damage comes more from overheating the target due to horrible heat dissipation in space instead of burn damage

[JoeSchmuckatelli]

6 minutes ago, ARS said:

If you mix oxidizer into flamethrower fuel, could you (in theory) use flametrower in space? How effective it's gonna be? I assume the damage comes more from overheating the target due to horrible heat dissipation in space instead of burn damage

Fuel + O2 does burn in space.  But I doubt you'd get much efficacy from it.  Not too many weeds up there.  If you're looking at a military application; I suspect there's much more efficient tools for those jobs.

 

This may interest you:

Watch NASA Set a Fire in Space ... on Purpose | WIRED

 

[kerbiloid]

If mix together a fuel and an oxidizer, ignite this, and point the nozzle towards the enemy, this will allow to

Spoiler

jump away and escape from the battlefield much faster, because that's what they call "rocket engine".

So, it's actually very useful.

[ARS]

32 minutes ago, kerbiloid said:

If mix together a fuel and an oxidizer, ignite this, and point the nozzle towards the enemy, this will allow to

  Hide contents

jump away and escape from the battlefield much faster, because that's what they call "rocket engine".

So, it's actually very useful.

LMAO

[razark]

Problem: I want to set that thing on fire.  Thing is some distance away from me.

Solution: I will use a device that throws flames at thing.

Result: I have thrown flames at thing, however there is no oxidizer available for thing to continue burning, so thing is not on fire but merely somewhat warmer than it was.

 

A spaceflamethrower should not use a mix of fuel + oxidizer sufficient for the amount of fuel, but a mix of fuel + an extreme amount of oxidizer.  The problem then becomes "How do I keep the oxidizer in contact with the additional fuel (thing that I want to set on fire)?".

[kerbiloid]

17 minutes ago, razark said:

I want to set that thing on fire.  Thing is some distance away from me.

Hello, Mr. MacReady.

Spoiler