MDF box vs. buying a new in-line fan

[omgwt]

Hey guys. Not sure where to post this but I'll make a thread to get the most attention

So I have this fan, TT125 Inline fan 220 or 280m³/h (I use mine at 220 settings)
I bought a speed regulator from ventilution - and it works pretty good - however I get this extra motor noise when using it - humming and rythm changing etc... I understand that this is normal - and it doesn't actually hurt the motor, it just gives this shitty noise that's annoying.

So I was wondering what my best plan would be - building an MDF box and silence it as much as possible - or buy one of those PrimaKlima fans with built in speed regulators and temp guard

These are the options I am currently considering, I guess the questions I have regarding these are;

Would the MDF box actually remove the humming/motor noise created by the speed regulator? (Think MDF @19mm thickness and 70mm rockwool on all the inside walls of the box, possibly bungee hanging inside the box if necessary)

And would a fan with built in speed regulator actually make a difference regarding motor noises and humming?

I have aucustic ducting so the air movement isn't the cause of my problems

Sidenote: I also have a TT100 fan with some cheaper fan regulator - but it also makes a ton of shitty noises - so I guess the same question applies there. If I buy a new fan I guess I'll get a 125mm for this setup too, though.

 

[queequeg152]

mdf is great at killing higher frequency sounds, but not good at all at low frequency stuff from what i remember.

if you can get acoustic drywall... you might put a layer of this drywall over each side of the MDF + acoustic glue.

idk though. sound is tricky.

 

[omgwt]

Yeah no doubt it's really tricky. I currently have a cardboard box filled with some aucustic foam and other crap like that - and it works decently to get rid of the noise from airflow - but does virtually nothing to the humming. I dont really mind airflow noise - it's that humming/random change of pitch etc. - that's killing me at nights :/

Hopefully someone has something to say about PrimaKlimas fans (or some other fan you can adjust the speed on without any annoying noises) - it's something im really considering but if it still makes that motor noise it would be $150 of cash I didn't wanna spend, hehe.

 

[queequeg152]

a properly sized fan is probably the best bet no?

what cfm are you running with the fan slowed down?

i have a few bathroom fans that are fucking silent... panasonic whisper flow or whisperline, i cant remember which. very expensive per cfm though.

 

[queequeg152]

could also just put the fan inside the attic space or perhaps a closet.

 

[omgwt]

could also just put the fan inside the attic space or perhaps a closet.

That's not an option.

I need a fan that's adjustable because I sleep in the same room, I don't really understand what you mean with properly sized fan, the fan performance is more than necessary when the light is on, but at night i wanna be able to turn it down so that i can sleep

 

[queequeg152]

oh i see what you mean.

i assumed you had an oversized fan and slowed it down to quiet it.

sound is tricky like i said... without knowing the frequency of the hum its REALLY hard to give you an answer as to what material.


i dont know SHIT about video editing or sound editing or anything... but is it possible to record the sound on a phone or video camera... and play it back in some software that could show you the dominant frequencys?

stuff low into the double digit khertz is the hardest to quiet down( think car stereo base). it penetrates everything... brick drywall, insulation, blankets...

i have some documents regarding noise in hvac systems i could share with you, but idk how. its a pdf document. it mostly covers noise from air movement and system effects, but im guessing its got some information regarding materials and such.

regarding slowing the fan without the hum... with single phase motors its very hard to speed control these things without issues because of how an induction motor works.

from what i recall ( could be wrong here, if so, sorry.) these cheap speed controllers operate by simple PWM switching in phase with the AC current. the inertia of the motor carries the rotor forward in between pulses.
these things are best on universal or dc motors like you see on polishing tools and shit... on regular split or cap start motors its a problem.

something strange happens inside the windings with the magnetic flux and these PWM oscillation causing this buzzing or humming.

what you really want is an ECM(electronically commutated motor) motor like you find in variable speed air handlers, and in newer VRF and two stage condensing unit fans.

shurly someone makes one in a smallish size... 400cfm? its just a matter of finding it, and paying out the ass for it.


the motor you linked earlier probably just uses multiple taps on the induction coil windings similar to how a ceiling fan operates. all windings powered on is your high speed. a single set of windings powered on is the low speed.

 

[omgwt]

That's interesting, I'll look into that. Perhaps you could upload the pdf on like.. jeez i dont even know any site, hehe. Well I don't think that should be necessary just yet but -

I was looking around and I checked closed on the fan I am considering - it has a digital fancontroller from GSE so maybe it's a correct sort of fan motor to change rpms without additional noise?

http://www.head-nature.com/article/06855/PrimaKlima-Fan,-built-in-GSE-digital-fancontroller.xhtml

Oh and yes I believe my fan controller might be a variac (not sure..?)

Anyway it's one of these I have; http://www.growin.uy/growshop/lampe...ion-drehzahlregler-230-240-v-400-w-1-8-a.html
Doesn't really say much, but yeah!

Obviously I want to find the cheapest route - but I'd rather get a new fan/fancontroller that doesn't create the humm - than to build the MDF box and still hear it from the fan i currently have - and then having to replace the fan.

But yeah, thank you again for the replies queequeg152

 

[omgwt]

Alright - I have made up my mind after finding EC fans - they are fans using that kind of motor you were talking about queequeg152, more specifically brushless dc motors

And I found them for around €130 each - which is right in my budget for now!

I am gonna order one and see how much noise it makes, but I think it will remove that disgusting noise I don't want!

Thanks again for the help, I probably wouldnt have looked twice at those EC fans unless you told me about the difference hehe!

 

[Mikell]

You can upload pdf as one of the options when replying though only up to 1mb (stupid limit).

 

[trichrider]

pdf s have links too....

otherwise how did you navigate to it?

 

[queequeg152]

no, this pdf has no link. its from a set of documents off of a cd.