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All of these cases have a big problem. Can you tell what it is?

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If you said the intake fans are starving for airflow,

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give yourself a gold star. This was a widespread problem in case design for years,

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but new airflow edition cases have flooded the market,

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completely solving it, or have they? See, there's nothing that Lee and Lee

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or Fractal can do about users, shoving their cases right up against the wall

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or on top of a shag carpet. You could be totally killing your gains, bruh.

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Killing your gains.

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But by how much? How much space does a fan need

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before it gets starved for fresh air? To find out, we sent Adam all the way

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to NASA's Langley Research Center in Virginia.

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Oh, sh! To work with some of the top scientists in America

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to figure out just how close is too close

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for good PC cooling. And how close is too close?

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For me to segue, to our sponsor.

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I know how I would try to answer our question, but where would NASA start with a problem like this?

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Great question. We're at the Hypersonic Test Complex

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at the NASA Langley Research Center, and we're gonna do some super scientific stuff,

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and that means we're using this tape and this string. I'm not even joking.

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This is called tufting, and it is decidedly low-tech,

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but it remains one of the most important forms of aerodynamic testing that can be done,

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and it's basically where NASA starts every single time.

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You see, air is difficult to study because it looks like this.

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So we rely on the way it affects other things

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to understand its behavior. Wow, I wasn't that far off.

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What you're looking at is a Noctua NF-A12X25,

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with some acrylic acting as our airflow restrictor or our panel.

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With tufts or little pieces of string on the backside of the fan,

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we can see how adjusting the distance of our panel from three and a half centimeters

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down to just 0.5 centimeters affects our airflow.

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We'll put the specifics up on the screen, and you can pause and read them.

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Actually, we changed our minds. It's an article on the lab's website. It's in the description.

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So what did we find out? Well, a few things.

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As you'd expect, at an ample distance from our panel, our fan performs admirably,

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sucking air in on one side and blowing it out the other. What I didn't expect, though,

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was that the tufts near the center only started to get a little floppy

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when the front panel got really close, just one and a half to two centimeters

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from the face of the fan. Another thing I didn't expect was that getting even closer

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caused the fan to not only blow in effectively,

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but even start sucking the tufts back into the blades,

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indicating reversed airflow. But it's a little hard to see like this.

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Oh yeah, I forgot. These are strings they glow in the dark. We took this big-ass NASA grade ultraviolet lamp

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to get maximum glow from our tufts while we recorded on this beast,

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the Kronos 4K12 high-speed camera.

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We're prepping our 1000 FPS 4K camera.

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That's about 11 gigabits per second of data,

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which means that recording on this for a minute is going to be bigger than your call-of-duty install.

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And in slow motion, we can get a much closer look.

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Note the increased tuft movement in our close-up test condition, indicating more turbulent flow.

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And you can even see some of the tufts dragging into the middle of the fan

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where there's areas of low pressure. Pretty cool, huh? Super cool, Adam, but we have Kronos camera at home.

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Why did we need NASA for this? We didn't, but for what we're going to do next,

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we sure did. And besides, if NASA invites you out,

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are you really going to say no? They were even nice enough to give us a whole tour

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that included an incredible new makerspace that they use for rapid prototyping.

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Our supporters on Floatplane get exclusive access to that and a ton of other content,

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so if you want to check that out, head over to LMG.GG slash Floatplane.

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For now, I'll just give you a TLDR. The Langley Research Center

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is kind of the OG NASA facility. In fact, it predates NASA itself,

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founded in 1917 as part of the NACA, which is the aeronautics organization

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that would eventually become NASA. The Langley Research Facility

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was keyed in numerous discoveries and improvements to early flying machines,

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creating the first hypersonic jets and paving the way for space travel

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and would go on to play a key role in the Apollo missions. Currently, one of the focuses of the research center

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is assisting the Artemis campaign to get to the moon as a means to get to Mars, pretty cool.

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A little bit out of the scope that we're going to be working on today. So we're going to steal a couple of the 3,500 employees

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that come here every day to do some more down-to-earth testing.

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We're inside of the Hypersonic Test Complex at the NASA Langley Research Center

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to answer that... Wait a second, this is the same lab?

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Yep, same lab. I thought we were supposed to go somewhere that was like more high-tech.

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Oh, it's more high-tech over there.

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Oh, right, and this is Dr. Lewis Edelman. He's a researcher here at NASA,

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and he's helped design all of these experiments that we're going to be running today.

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Hello. So what the heck are we doing? So we've moved on from tufting

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to particle image velocimetry, or PIV.

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Oh. Flashing lights in fancy cameras. Sounds like my kind of deal.

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First, we shine a bright light focused

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into a thin vertical sheet. Then we fill the air with, you guessed it, particles

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and start rapidly taking pictures. Now, that might sound like video,

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but it's different in one important way. Instead of taking images at a constant frame rate,

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we instead take two samples just microseconds apart,

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followed by a short gap, then another two samples,

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and so on and so forth. We can then use really clever math

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to determine the velocity of the particles. Note that this is not speed, but velocity,

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because we're talking about how fast they're going and also their direction.

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Sounds simple, right? I mean, not really, but for starters,

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the particles we're tracking are not air, which means that they won't move exactly like air.

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Second, to do this right, we need the velocity of many particles.

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That means thousands of samples across thousands of images.

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And third, we need some pretty special cameras.

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The Levision Flowmaster is a super high precision machine

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that uses a double frame buffer to take photos just nanoseconds apart.

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All right, it's finally time to test.

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Hit it. So this is our first test result.

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I mean, there's no obstruction on this fan. No obstruction, pure control.

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So we're doing the analysis now on one image pair

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as a test for the processing stream, and we go, okay, that's not very clean.

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Once we take an average of the 200 or 158 images

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we just took, this will fill out to look like a fairly nice picture.

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Importantly, that this is kind of the hub, like we're really only looking at the top half

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of the fan right now. We're looking at the top half of the fan. Would it be fair to expect that there would be,

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I mean, it's a circle, so there'd be symmetry on the bottom? I would expect radial symmetry in all things

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you wanna try and measure in as much detail as possible. So if we were fully zoomed out

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and looking at the whole fan, we'd be wasting resolution effectively.

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So this is it, applying the scaling from pixel space to physical space

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from our calibration plate. Now it's starting to do the PIV,

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and we can see for our 158 frames,

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that's probably gonna take about 20 minutes. What is this computer running on?

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This is a

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i9-14900K with 192 gigs of RAM.

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So this just takes a long time, is what you're telling me. Yes. After considerable number crunching,

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we've got our results, and what you're looking at is a narrow slice of air

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that is flowing out of the fan. The colors indicate the stream-wise velocity of the air,

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so how fast it's going away from our fan blades,

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and then the arrows are kinda just an easier way to visually process that same information.

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Then to make it even simpler, we added these dots. Without a front panel, flow is smooth and fast moving.

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There's a small section where you can see there's no flow, but if you look closely,

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that's right behind the fan hub where there are no blades.

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Now, it is important to remember that this is just a thin slice of the overall airflow

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in what is a 3D space. Our test isn't gonna capture

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the spiraling 3D vortex of the air, but the overall direction away from the fan

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is what's most important for cooling, so this is good enough for our purposes.

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Fun observation, by the way. Dr. Edelman noted that the way that Noctua's fans

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throw momentum inward more than a typical fan contributes to reducing their overall noise.

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Good job, Noctua. When we move the plate closer, we don't see much change.

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That is, until, just like in our Tuft test,

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we get as close as about 15 millimeters. Take a look at how large our dead zone has become now.

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We also noticed that the flow of air is starting to curl outward

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rather than coming straight out of the fan. What that means is lower stream-wise momentum

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to blow air across your components or to pass through a restrictive heat sink or radiator.

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But why? Well, it's due to the difference in radial pressure.

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The air that passes through the tip of the fan blades is lower pressure and almost bounces off the stagnant

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and thus higher pressure air that's right by the fan hub.

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This isn't optimal, but our overall airflow

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is still pretty good, so for a case fan,

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it's probably still fine to have this much restriction. We will check on this test condition again later

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once we add a radiator. For now, let's look at our worst case scenario in open air.

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Imagine your case is right up against a wall or your power supply intake is on the floor on a carpet.

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This is what you're doing to your poor, poor PC.

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Not only is the fan barely pulling any air in at the edges,

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it is so starved for air that there's a reverse flow

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that causes the air to curl into a vortex that isn't gonna move heat anywhere

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and that's your best case scenario. What if we were trying to cool something directly

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with our starved fan? To find out, we whipped out a water cooling radiator

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to create a scenario with much higher back pressure. You can think of back pressure as the friction

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that a fluid experiences in movement, and as you can see, adding a ton of friction

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to an already restricted fan results in a two-word review of my debut rap album, Zero Flow.

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Now naturally, backing this off to a 15 millimeter gap yields much better results,

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but it's still worth noting that this is a massive drop in performance compared to our free air test,

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especially with respect to the size of our dead zone over the fan hub.

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Practically speaking, we're only getting flow on about the outer 50% of the fan blades.

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Interestingly though, the radiator completely straightens out the flow

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and we don't see that same outward curling, but the speed is cut about in half.

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So what does all of this mean? Well, we can't draw overly broad conclusions.

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We only tested the NFA 1225 at full speed, but it seems like you can get as close as about 15 millimeters

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or a little over half an inch from your fan with reasonable performance.

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Any closer and you are seriously harming its cooling ability.

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An obvious question would be, why go to all this trouble?

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Couldn't you have just sent a piece of acrylic and a fan to Cybernetics to put in front of their fan tester?

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Well, yes, but also no. While a fan tester would tell us the performance

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of the fan under various conditions, we were more interested in measuring the behavior

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of the air, which tells us not only the answer,

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but it also lifts the veil on why the answer is what it is.

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It also gave us an excuse to check out another really cool piece of kit down in Virginia.

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If you thought air was complex, we'll just wait till human perception gets involved.

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Yeah, we're gonna talk about sound. Now, we have been hard at work improving

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our audio testing at LTT Labs. I mean, we even just built a home theater room

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to test more speakers now. But what we don't have is a NASA grade audio chamber.

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This is the shack and it's a little old place where we can do some testing.

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The small hover anechoic chamber was constructed in the late 80s and it gets as quiet as 18 dB,

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which is disconcertingly quiet.

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For our testing today, we're using two different arrays, a linear one up there and a spiral one.

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Why are they different shapes? Well, they have two different jobs. The linear array is a directivity array

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that gives us a broad idea of where sound ends up in the chamber.

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The spiral array, also called a phase array, is a collection of 40 beamforming MEMS microphones

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that allows us to get super detailed information about the source of a sound.

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These microphones are so precise that we can map the location of the sound

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onto footage from the camera that sits in the middle of the array.

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Essentially, you can define a region in here and it will perform an integration.

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So right, it's a little hard to see, but right now it's just region one, two, and three.

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And then you can basically go ahead and have it process it and give you a spectrum like this

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with the different contributions of those regions to the total sound field,

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or at least what their array picked up. Why would folks at NASA need to know this kind of stuff?

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Well, when they're testing the acoustic properties of something, they want to know where that sound's going to be coming from.

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Like this, for example, they might want to understand if the sound is coming from the tips of the blades

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or if it's coming from the rotor itself. There's only one way to find that out,

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and that's to use the phase array. I mean, there's probably another way to find out,

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but the way we're going to do is the phase array. So stop asking questions.

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Well, you can ask one more question. If you noticed, our fan is looking a little pink.

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Why would folks at...

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That's because this apparatus was designed to test rotors for things like drones.

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So our NF-A12X25 that we were using before,

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it was a bit too quiet, and we swapped it out for this industrial version

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that runs considerably faster and considerably louder. The paint that's on it is this funky pressure sensitive paint

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that we were going to use for another test, but we ran out of time

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because NASA has a lot of important work to do. Anyway, I bring up the paint

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because it might make the fan perform a bit worse than what Noctua would ship from the factory,

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but we aren't comparing it to other fans. We're only comparing the intake clearance,

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so we're not worried about that. Again, because of time constraints, we decided to just test the fan without the front plate

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and at the 15 millimeter point. Now, intuitively, you might think that covering a fan

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would decrease the amount of noise that it makes, right?

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But if you've ever tried placing your hand in front of your PC fan, you might have noticed that it often gets louder

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up until the point where it becomes completely started there. And in our test conditions, that's true.

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You can see a broad spectrum increase in noise when the front panel's present.

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Why? Well, referring back to our PIV results,

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remember the stalled flow in the middle? That causes the overall airflow to be more unsteady,

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which makes it louder. Think of it like roaring rapids

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versus the smooth flowing water in the Mississippi Delta.

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And this increase in noise also shows up in our phase array results.

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Yet another reason to not let your fans get too close to obstructions.

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Even if you have cutouts in the side panels, those can still cause annoying resonances.

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Fractal terra owners will know this very well. In summary then, for performance,

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keep your fans more than 15 millimeters away from any surfaces and 20 millimeters or more

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if you're gonna be contending with other obstructions like a heat sink or a radiator.

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As for noise, it seems like you can't have too much clearance from the intake,

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but you can definitely have too little. There are a hundred other questions

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we would have loved to answer, but frankly, NASA was already extremely generous

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with their time and they are hard at work answering much larger questions.

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This may not have been the be all and end all answer that you were looking for,

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but that's just how science is. It's the accumulation of many tiny discoveries,

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solving many tiny mysteries that build up to create a knowledge base that allows us to

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have a greater depth of understanding of the world that we live in.

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Before we go, I wanna thank all the folks that Massa, who helped made this possible,

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Lewis, Brittany, Nick, Jordan, so many more folks that I haven't named

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helped make this trip possible. Thank you so much. Thank you for watching and of course,

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thanks for the segue to our sponsor. Thanks for watching.

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If you like this video, why don't you watch another one of our videos where we tour some cool place,

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like how about there's an internet exchange in Toronto

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that was pretty dang neat. Thanks again to NASA. Thanks for watching.

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Bye.