If you make a hollow box that the air flows through and fill it with a dense "wool", like those copper or steel "scrubber pads" for the kitchen, you should be able to reduce a lot more noise! The small heavy fibres will help absorb the vibrations... Printing the muffler enclosure out of TPU would probably help as well as, the rubbery material will dissipate the vibrations as heat rather than reflecting or transmitting them!
wait what ? you here ? hehe nice to see you here. Im not sure if you remember me, but I sent you a cad of your awesome knife. I wanted to print it for a prop, but we both agree I should not publish it. Im honoured to see you here my friend
@@Vez3D haha I apologize, my memory is like a sieve so I don't remember, I barely remember what I did this morning 🙂You are veery welcome to print the model for yourself, but not sharing it is a choice that's greatly appreciated! I've been watching your videos for a while! I LOVE what you are doing with high speed printing! Let me know if you ever need someone to bounce ideas off!
As an audio professional I’ve analysed the audio coming from the video with a spectrum analyser and the electric motor from the cpap is putting out 19khz (19,000 hertz) frequency when the fan is running the whole time but when you put the muffler on and off there was about a 5-7dB difference in the 4khz range from the intake noise. So the baffled muffler did work! You probably wont stress too much about the motor spitting out 87dB at 19khz as its very high on the spectrum in regards to human hearing (80-22,000 hertz). Hope this helps!
I was going to do the same thing. That was about the difference i heard in that fs band and i was going to analyse it, but thought i would check and see if someone else had first. 5-7db is quite significant in that band. So like 400% less noise power in the midrange. I would say that is a very good start.
This is a little biased in testing because your not dealing with the sample but his recording equipment, youtube sound processing and then speaker output. He menations he doesnt hear a difference as well. Other aspect is what his phone microphone picks up as well. Overly simplified test with areas to.improve but at least hes quantifying.
@@jeremyglover5541 yes, the 6dB noise reduction means approx. 4 times less noise power in the midrange , and the minimum 3 dB noise reduction overall means 2 times less noise power. Excellent results from this simple solution
@@DoubtingThomas333 Sorry, sadly my ears are not factory calibrated, so I can't discern a frequency spectrum by just hearing it so I need to use tools to know what frequency a sound muffler affects and how to proceed to reduce the strongest frequencies or at least the most obnoxious ones, god I wish I was born with an spectrum analyzer.
I haven't tried a CPAP purely cuz I didn't want to hear it. Now you've got me brainstorming from my Automotive experience. An inline resonator on the outlet of the pump may help as well. A full "Airbox" with the pump inside, and maybe some insulation / a fillter to prevent sucking in any sound dampening materials. My wheels are spinning now Simon...
The dB reduction might be small, but it's not a linear scale so it's still a lot -- and it sounds better, so I'd call it a win! I have my remote cooling compressors in a padded box and it's great for noise. A larger air space around the baffled tube (between the baffled ID and the overall OD), and especially stuffing that space with something soft (cotton, steel wool, etc.) would probably help this design kill even a bit more noise, but you're dealing with a high-RPM impeller and that's always going to be tough from a noise perspective.
@@nyeleskettes Source for this? Perception doesn't change the fact that dB is a logarithmic scale and every +10 is a 10x increase, -10 a 10x decrease. Normal conversation is about 60dB, a vacuum is 75dB ... that's "only" +15dB ...
Its a bit of this and a bit of that. Yes its frequency related, in that the shape of our ear means we have better or worse response in level at different frequencies and that is different for everyone. But yes, a small difference in db is a large amount of actual noise power. 3db difference is half
@@nyeleskettesIt is definitely not linear in terms of perception...the difference between voice and a vaccine is the same between a vacuum and a jet engine...
Another thing to kind of mention here is you also have frequency. You may not see big number changes on a dB meter, but suppressing a frequency can make all the difference. You often see that in a lot of household appliances where they can only do so much with the parts they will have to use. Hair Dryer, Vacuums, Blenders, Computer Fans. Which I believe you accomplished here and mentioned in the removing the annoying noise. Otherwise you will start to quickly get into other things needing to change in order to reduce noise, larger inlet/outlet, slower fan speed, blade geometry, less restriction. Which I think in this application can only go so far.
What also could help is rubber mounting the fan. Some printed TPU standoffs or something that lessens the vibrations of the fan. Like some Computer Case fans come with soft rubber gaskets for mounting to dampen vibrations.
Simon excellent solution! You could also print some T-spacers and TPU washers to install on the CPAPa mounting screws (which insulate the contact surfaces including the screw itself). This would drastically reduce the vibrations and therefore the fan noise on that aluminum plate and put together with your solution you would certainly remove other decibels. another optimization is to coat the walls of the airbox with adhesive sponge, you do not compromise the airflow and further reduce the noise
Sound reduction is hard, but what I've found works best is to isolate vibration as much as possible, so soft surfaces, lots of mass and shapes that "eat" noise. And generally you want to make things as air tight as possible. If air can get through, so can noise! With airflow in mind, I lack the knowledge, but looking forward to see what you find!
I found on my CPAP setup that there is also a lot of noise coming out of the duct, so I think both intake and output mufflers would be even better. And decouple everything with soft TPU 'gaskets' so that vibrations and sound don't get transmitted. Also put some wool or whatever that stuff that is used inside loudspeakers is called inside. Maybe also make the plastic parts and backpanel heavier like the car audio guys do with that black tar stuff or whatever it is.
I'm not a sound expert either but I believe that to improve even more the noise reduction (based on the automotive again) you should put mineral wool inside between the two layers of your resonator. Another idea that could work is making a sound maze, again with some insulating material on your walls. Maybe you could even experiment with the expending pla that seems like foam
I would design it as 1 part standing on the end of the air intake so that the resonator could be sized to the max of your constraints, the plastic wall thickness did not leave much room for expansion. Try varying density and thickness of whool or cotton balls to see how much they restrict flow and reduce noise at the intake.
I heard more motor noise being transmitted through the solid mounting plate that you have your blower attached to. Maybe a TPU gasket between the blower motor, the mount, then the muffler? Also, maybe some sort of gaskets/grommets for the bolts to further minimize vibration transfer?
Measurement problem here, you could actually put it where you stand, for example 50cm - 1m away from the printer, because the chamber creates an echo of some sort and this why we can hear it in the camera but the tablet shows still pretty high DB. Better measurement for NOISE is a measurement called "sone", it actually shows you the noise instead of the pressure of the soundwave :)
good point !! my best measurement here was my ear meter :P and my ears are telling me it helped a LOT so I am quite happy with this. though there are room for improvement for sure
I agree with Damian. You actually loose 6db every time you double de distance. So a small 3db reduction near the CPAP will actually be more like 6db outside the printer. The reduction is exponential, not linear. That's why most of measurement in spec are donne at minimum 1meter from the sound source.
Some Ideas from and things i noticed as an audio engineer and someone who does measure sound pressure levels at concerts for a living: With the first airbox design the metering that is connected to my speakers shows around 3dB of drop. Maybe the microphone of the tablet is already maxed out and the actual level is higher than the displayed 87db? With the final design my metering shows also like 2-3dB more reduction than yours could be the same reason. The resonant absorbers are tuned to a specific frequency and are typicly used for lower frequencys. If you take a look at the spectrum of the noise from the CPAP its pretty broadband from 500Hz and up. Your design still works but may not be the most efficient solution. My take on a muffler would incorporate 3 main principles: 1. building a maze so there is no direct way for the sound to escape and it has to bounce around the corners 2. lining the inner surfaces with some kind of acoustic foam, like you have on your wall, to absorb the sound energy that is bouncing around 3. making the corss sectional area bigger to reduce the airspeed to reduce turbulence inside the muffler which would otherwise generate new noise. But in the end i may be wrong since this is a much smaler scale than i use to work with. And it may bee good enough as is since on my printer the noise from the air hitting the actual print is much louder than the noise of the membrane air pump and the only thing that would help would be a rock solid enclosure for the whole machine. :D
So as a VAG expert (Volkswagen Audi Group) one thing I've learned about the way the turbo muffler works is the air will pass directly through this baffle instead of around it and then in it, a hollow chamber is surrounded by it disrupting the direct flow path of air, allowing it to bounce around and off the larger half before it exits out the other side. This will indeed remove some velocity but for turbocharged vehicles, it increases back pressure a bit and gives lower end torque.
So, "baffle" and "perforated" are both appropriate words. However, I think you're missing a great opportunity here. You have an ability that most manufacturers don't, the ability to print complex and convoluted structures inside your silencer tube. Old school hot rods would use an exhaust like that packed with glass wool to kill the worst of the higher frequency notes, you can use anything you can think of since you have no temperature constraints. Maybe an open gyroid infill? Maybe a TPU egg crate? Maybe try to wrap it in the triangle traps they use in acoustic deadening panels for recording studios. I would definitely suggest sending the air down an 'S' bend surrounded in a soft, porous material of some manner, to try to absorb the sound, as opposed to a hard shell that wants to reflect the sound. Also, decibels are on a logarithmic scale, so remember that dropping by only 3 decibels is a reduction of the sound energy level by half. That's a big difference.
I think the word he was probably looking for, for "perforated holes", would be "perforations". A "perforated hole" would be a hole that has holes in it.
In my experience and learning, I have understand that a lot of noise comes from the body too, as you said in the end of video and a lot comes from the exit too. So you have to work on almost three sides, intake body and exhaust. Tankful to RU-vid I encountered a video by Dyson where they explain how Helmholtz resonators can drastically change your life (not only in a mastering studio), but the way is lastricate of pain for the earth due to waste of plastic in try. If you find an audio meter that gives to you the frequency spectrum too, you can understand where is the peak in frequency, but it change with the speed of the fan and air, so you will have problems to make the right Helmholtz or you can make a screwable volume and put the right one on the silencer in accordance with the load and the frequency. Easy to say but Dyson level to do.
@@Vez3Dthen add some pimping from the end of the tube to the inlet of the fan, and put the foam inside. It should absorb the noise without perturbing the airflow
@@Vez3D imagine it was just like an air filter, enough to drown out some of the noise and then still enough to let the air through . and not like a KN filter that make it hum a little more :)
Very interesting implementations of designs from cars! What you are missing out in your implementations is how much noise goes through the hard shell of your muffler and through the fan enclosure itself. You should try simply making any muffler from a foam material or at least make a foam gasket and connect fan and also a box only through such foam gaskets. The noise you hear is only 30% from the air flow, 70% is from the fan mechanical parts, bearings etc. Also if you think of your own solution instead of just copying existing car designs, I am sure you will come up with something better :) For example make a helical entrance into the fan intake to help direct air into a spiral before it enters the turbo impeller section, this will reduce air noise significantly more than these 3 designs, due to much lower turbulence. With all that said, I never run any of my printers in the living area where I or my loved ones breathe, so such noise isn't an issue for me. Cheers!
Very cool! I would: - remove the centre parts of the cpap intake, (i think they play a good role in setting the frequency/pitch of the main noise), if possible. - on the third design, shape the intake regions more like the turbos intakes. ("roundy", not as straight nor deep as the ones you showed first). O.D. = 2 x I.D. with Assimetric Conic Rho fillet. Pls do a follow up! :) 💪💪
Hello! The idea is good, but not really. 1. You change only part of the sound that creates the flow when entering the fan. 2. The main sound is emitted by the fan motor itself, which rotates on bearings and creates vibrations. You increased these vibrations when you screwed this fan onto the back wall. It works like a resonator and amplifies the sound like a guitar drum. 3. Some of the noise you hear from the pipe. The pipe comes from the fan and has a spiral shape inside. This inner surface creates turbulence and increases noise. But. The main noise is transmitted to the pipe from the fan through vibrations. 4. You reduced the inlet section on the fan with your device and allowed the air direction to change at an angle of 90 degrees. This greatly increased the turbulence at the inlet and worsened the fan parameters. 5. Most of the noise comes from the fan blades as they don't work 100% laminar. I propose: 1. Remove the fan from the rear wall and place it on soft rubber damper pads 2. Wrap the outside of the fan housing with soundproofing material, as soundproofing is done in a car. 3. Make a different shape of the suction pipe into the fan. It should expand at the beginning and narrow down to the fan inlet diameter. The form must dampen the sound waves that come from the fan pipe. I have an idea, I'll draw it. 4. After the fan, you need to put a device that spins the flow and makes it straight, this will reduce the sound. I'll draw too. 5. Well, the fattest. It is necessary to make a different shape of the fan blades, more precisely, add ridges (ribs) to the surface of the blades, which will divide the resulting parasitic vortices on the blades and reduce noise. I don’t see from the video what kind of fan is there, so I won’t draw it. What is the shape of the blades? Centrifugal or axial? Write
Excellent write up. Im glad im bringing this project on the table as I was sure people would cooperate and give advice ! Thanks. Share back your design please
The 3D printed "Exhaust tube mount" will probably also add a lot of turbulance, since there is a sharp edge where it connects to the tube. Using ABS for that part and smoothing it and adding a radius at the end of it will also reduce noise.
If you use TPU for the baffle and housing that will absorb the sound more effectively than the resonant prone PLA. It’s like adding cotton or sound absorbing material
I'm ordering a CPAP next week, and it'll be fun experimenting. Will still take a while though, as I need to get it from China, and shipping to Norway will take a couple of weeks.
Yeah I had a very similar issue adding a velocity stack to my part cooling. The dang thing just got louder and didn’t push anymore air. I think the amount of work to go from a velocity stack to a very well optimized velocity is more than just adding a horn to a fan. Great work though. I always appreciate your willingness to push the limits and make better machines.
The dB scale is logarithmic you basically halfed the noise but the corrugated hose isn't helping one bit. For my actual CPAP machine for my nightly use, i swapped the hose out with some clear silicone tubing of equal ish diameter meant for fish tanks. And 3D printed fittings to make the connection points perfect. Made the CPAP more comfortable but also naturally quiter and WAYYY quiter when moving around.
Firstly every 3db of drop is half the noise level so actually your designs are doing well. As people have already mentioned there are frequencies that people pick up on more than others so moving the frequency to something "less annoying" can be just as useful. my two cents would be that your trying reduce the noise of an intake and alot of noise can be created by not having a smooth path into the centre. I would suggest a Bullet to smooth the hub and a nacelle around the perimeter. Definately would isolate the fan from the aluminium back panel
@@Vez3D I am messing with you ;) in the video it sounds like you say "furriest" which is something very different from "furious". And nice, have watched those movies way too many times...
Output noise is also a problem limiting what you can get to besides getting pesky peaks even if you completely removing intake noise source.... I have a office with too outside walls just begging for one of my projects to ether move cooling radiators, pumps or air output systems physically away with thick walls etc. making efficient gap. Thermal systems also have the option of going down - including the pumps - just get into the earth if you are at ground level, don't have anything under there yet, hate your floor and own it all - this is underrated especially where winter might be a problem or summer heat might not provide cooling. Just add lots of surface area that isn't insulating but can handle the liquid, moist earth and the pressure. Also remember to consult experts near load-bearing walls.
Look up Helmholtz resonator. You are on the right track with the dual intake air box. You need to tune the length of the pipes and the air box volume. You will be getting audio leaking through the walls of the air box. A Helmholtz resonator will suppress wideband noise.
Well done Simon. I think that's a great option to reduce the annoying noise. I do wonder if the CPAP motor itself is vibrating the frame. Maybe in another attempt, a TPU soft mount and housing should be designed around the motor. But at that RPM and air speed, its going to be loud no matter what.
Aluminum is a very resonant metal, consider shock mounting the blower and applying damping (dynamat or equivalent) to the flat aluminum plate and blower housing
I don't know many details about your machine, but have you used any sort of dampening mounts for the air blower? Some of the noise might transfer any loose parts through the frame of the machine.
I say add some polifill (pillow stuffing) in the resonator section see if that helps. Also the trumpet angle was too steep. Its needs to be more gradual. Maybe a horn but with hexagonal channels to straighten the flow before it hits the blades?
i have been running a cpap and your mount on my ratrig.. and the high pitched squeel these produce at 70+% is super annoying, and not comming through on camera how annoying and loud it is... i will print this as soon as i come home today :)
The thing about a lot of these solutions is that they aren't really Db solutions. It's more about the frequency. Certain frequencies are grating on the ears.
Not an expert, but I assume that a corrugated hose is normally used at a flow rate such that you get good laminar flow through the centre. If you push air harder, aren't you better off with a smooth hose? Less back-pressure making the fan loud and maybe less noise coming from air flowing in the hose?
Where's the mic on the tablet? If it's close enough to the input, it might be picking up its own wind noise that's making the results not really representative of the true volume. I wonder because it really sounds like the volume difference is a lot bigger.
Maybe try using a metamaterial print like the one that boston university came up with? It doesn't block any air at all but blocks up to 93% of sound depending on the frequency. You could also try to noise cancel it like headphones do. Companies do it by playing the opposite frequency to cancel out the current frequency, and that noise cancelling technology does best with windy noises, I think it would be very promising!
I've never really messed with using a CPAP machine for cooling on a printer but I do have some experience with CPAP machines for their original purpose and they're nearly silent. What about the modification that you've done with this one removed that original designed in silence?
CPAP has a lot of pressure, on one hand you can get crazy with the duct design (example: Hevort tentacool), but on the other hand you have a lot of noise. I think I would prefer a double 5020 toolhead with optimized thick and short ducts, graphs say that the airflow (that is what actually matters) will be roughly the same, pressure will be a lot lower but so will be noise too. Pressure only gives you freedom for crazy designs with a lot of restrictions without big sacrifices, but at the end of the day only airflow matters.
@@Vez3D It's a trade-off game, a little more weight but maybe more rigidity (as you don't have a flexible tube to move around). And of course absolute silence in comparison!
im curious what would happen if you combined a more dramatic air box, use a trumpeted design for intake, and have a resonator combined with air box. That sounds like it could work?
Turn the baffle to point into the corner, cut a circular hole into the glass and add an intacke tube to the end of the baffle so the air comes in from outside of the chamber, but the intake becomes longer to reduce the sound
Need to determine the frequency of the sound and focus on blocking those or dampening that area of the spectrum. Need @Hexibase to do an analysis for a vz-bot review. @Tech Ingredients also did a great breakdown in the speaker build.
Hi, as an audio engineer I can say that dBm alone will not really tell you a lot, you do need a spectrum analyser to get the full picture, when it comes to "wind noise" especially at higher feed rates the "whistle" that you eluded to is where the actual irritation comes from. To quell that noise, your box where the resonance is changed will need to be adapted, you are looking to get rid of a high pitched noise, what you could do is simply just line the inside of the box with a thicker material like a soft foam or even perhaps a cotton towel, same as you use to dry yourself off with once done showering it must not have a smooth surface or a shiny surface, DO NOT (as others have suggested) use the material as a filter as this will suffocate the inlet, it will make it quieter but will decrease the performance of that small fan severely (it does not have a lot of mass so does not carry enough inertia to keep that flow of air when restricted), but rather just use it as a damper, the small diameter throat will also cause more noise as this is where the inrush of air is buffeting, to cut down on this buffeting you need to design in two or more baffle's that also has a soft material glued to it the material will dampen the high pitched whistle easily you also need to increase the size of your inlet to not restrict the air flow. I see some posts saying to use mineral wool, do not do this, the wool degrades and decomposes and also after cutting it there are a lot of loose fibers on it that will go into the prints or can cause clogging this wool is fine for audio applications but not for air assisted applications, You can test this by getting a frequency oscillator app for your pc, run this at about 4000 to 12000Hz (4K - 12K)and then hold a towel in front of the speaker and yourself you will hear the difference. I would say a baffled intake with an oversize opening and a soft material lining should get you 90% there. Also, there could be a lot of noise coming from the part cooling nozzle as well, Maybe an inline baffle can help with this. Good Luck!
those sound levels are like genuinely dangerous long term! I think you also need to worry about the actual motor vibrations (dampening the mount) a bit too plus the output is very restricted and i assume a huge source of the noise also i feel like if we had knowledge to calculate the shape of those intake boxes it'd help more? audio science is .... hard
There is a noticeable change with the resonance chamber. Is it possible your measuring device is picking up internal noise since it’s resting on the unit?
That's a tiny fan at super high RPM. Why not try a larger fan for more volume/air flow overall on the back panel? Probably not a lot of space back there, but probably could make it work.
I once started wondering if bottled air might be quieter than fans, the cost could be lowered if I could fill the bottles from my compressor or if the tank on the compressor is large enough to hold enough air then it might be possible to pipe the air directly from the compressor without it having to start up, of course this is all dependent on the part size, my compressor is in the storage part of my shed/workshop and although it is in a separate room with insulation it is very noisy, it doesent take long to fill its tank though.
Moving air problem, like drone props fans make noise depending on the RPM and blade design, to keep the pressure up but reduce the noise look into the blade design in your spare time...
It isn't just the intake that is making noise. You need to put the entire CPAP housing in a sound isolating box. The motor is making most of the noise. Then have the intake/exhaust go through a mufler. The intake baffle works fine. I can tell the difference of the INTAKE noise being reduced... Too bad the CPAP motor is completely drowning it out. Motor and turbulence of the air inside the compressor housing are your number 1 sources of noise not the turbulence going in to the intake.
@@Vez3D By chance, have you already made a video that explains how the duct compresses the air and optimizes air flow / pressure? Or do you have some other pointers that could help me design a better duct for my printhead? Thx!
Would be good to use a spectograph to see the freqnecy distribution of the sound. Because the airbox did sound quieter, this is likley because the sound became lower pitched. Higher pitched sounds are perceeved louder than low pitched sounds by humans
The most effective thing you can do is use a bigger fan. This increase the surface of the intake and keep the fan speed lower. This is why pc builders allways look for bigger fans and lower rpms...
Question: have you tried to do the test without the drain tubes to the nozzle? I have the impression that this tube generates more noise due to the impact of curves of the spiral walls - it disturbs the flow of air and hence more noise.
I think, perforated ring can be a metal. Also, i placed outside material like sound barier in automotive sound technology. Thinkness app. 10 millimeters, but it also how you will deside... How it work. Air laminar flowing from high outside volume thru the holes and accelerating to the end of cone. Turned back sound wawes is quieting from sound isolation material around inlet. The inlet must do not touch the frame or body of the printer. No vibration transfer. I think, you have glue or flange the inlet to the fan... Have fan! The outside laminator have almoust same principle. You have unwind the flow after your fan and flow it to a direct channel. Let me know about your axial or centrifugal fan///
I'm no expert, but I have opinions and ideas that may help. Firstly, this is a strange way to try to fix your problem... i; personally, would have tried to find a fan/blower that was quieter out of the box, perhaps with better hydraulic ball bearings, or I would have purchased another blower and run them both at 50% which would be virtually guaranteed to give improvements. Otherwise, I would have taken into consideration that placing any kind of plastic form on the inside of that hole in thin sheet metal was doomed to fail, theres alot of air still getting sliced by that sharp punched hole and sheet metal aluminum itself resonates sound in an awful way, a plastic insert with a hole would have been better (think of what a speaker port hole looks like) and a soft material (tpu with lots of infill maybe? Another material?) Would have improved resonance... I may have even given the internal cavity a dimpled golf-ball like texture on the inside to reduce drag/ friction, lower resonance and maybe even increased airflow.
I designed one like a silencer on my JUBILEE printer and it works really well: 10dB reduction with small flow reduction, but need one in the input and one at the output
hi please excuse the google translation. I'm also studying a method to make the fans less annoying. there is a way to eliminate annoying frequencies via Helmholtz resonator
@@Vez3Doh okay!! i heard it on some 3d printer discord, you know how they can be 😓 for the aluminum parts as long as i keep your logo and i assume buy from mellow that makes sure it's okay? i would have done that anyway but i want to be sure as i respect you a lot c:
@@spindlywebs you can totally make your own parts and remove the logo and do all you want.. hehe its YOUR printer. What is not allowed is selling/commercializing it without the proper agreement. Its licensed non commercial, but you are free to do what ever you like with the CAD and have fun. Its exactly there for that.. having fun and if you can make it better, go for it and share back :)
@@Vez3D awsome! and i would never want to commercialize something somebody else made, open source is the way to go for everything imo (patents to cover r&d though)
yeah I say it at the end that we could enclose the full fan in a insulated box etc.. but I just wanted something real quick that anyone can print easy and install in no time on their VzBoTs. And it works quite good I think
Just grab larger turbo and run it at lower RPM. It will be quieter with same airflow. Why that intake sucks hot air from chamber? The cooler air will be ther less flow you'll need to cool down the part.
