Inline fan Noise Reduction: The Best Guide so Far [Dec’18]



Fan noises are irritants. And when it’s from the inline fans of your grow room, it’s even worse. Because you can’t either turn them off or live with the buzzing noise.

Fortunately, growers had worked hard to make noise reduction fairly easy and simple. As results, inline fan noise reduction from 85dB down to 60dB is nothing but a few steps away from you. All you need to do is acknowledge the ways, and choose your way of doing it.

And in this post, we’re going to tell you what exactly are the methods and how to adopt them for your grow space.

How Loud Is Too Loud?- Checking the Sound dB

Inline fans are great in use. But they’re way too noisy to keep in an indoor system like grow tent.

But, how loud is too loud as long as inline fans are concerned?

Well, the answer might vary based on the location, type of fans, the length of ducts and many more. But for now, let’s get a generalized answer-

dB meter for grow room noise

Usually, when the noise level crosses 75 dB, we take it as too loud to tolerate.

To check the exact noise level your fan is producing, use a dB meter and place it in front of the air flow once the inline fan is on.

If you find the score anything between 70-85 dB, you need to read the rest of the article carefully.

How to Reduce Inline Fan Noise- 8 Actionable Solutions

Okay, here comes the heart of today’s post, the 8 steps on how to make grow room fan quiet. Let’s start one-by-one

1. Isolate The Fans with Carboard/Wooden Box

One of the simplest, but working strategy to lower the noise of fans down is to enclose them with a noise-absorbing surface. We’re talking about DIY boxes made of cardboard, wood or any hard and rigid surface that can absorb sound.    

But many can do a mistake of keeping the boxes in direct contact of the fan. But that’s not just a smart way to do that. We suggest you to suspend DIY fan silencer box from the ceiling and walls. Although this process will cost you a little extra effort, but the result will be fabulous. You can use some bungee cords to suspend the boxes over and none of the vibrations and noises will come out of the box.   

Also, there is ready-made inline fan silencer box available in stores and Amazon. Can be a good choice if you don’t want to take the hassle of making it all yourself.

In together, noise-absorbing boxes suspended from the roof will absorb a decent amount of noise, and prevent vibrations to go through walls. Hanging stuff from the ceiling may come handy, and you may need to install a joist in this regard. 

Wooden Box for Inline Fans
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2. Get Your Fan A Speed Controller

Speed controllers are great! Especially when you want to get rid of the shattering noises when the fans run at full swing. What it does is, it gives you the liberty of dimming down the fan and have a control on the noise as well.

But there are a couple of cases that you need to watch out-

First, if you purchase a wrong grow room fan speed controller that’s not compatible with your fan. You may see the controller in action for a while. But that’ll not operate within the safe range of volts. Result? The premature death of your growroom fan.

Second, when you get to slow your fan down, you might not be able to meet the ventilation requirement of the growing system. Also, the temperature may rise high. So, you should either buy additional inline fans and use speed controller on that also. Or you can switch some other methods of noise reduction in this list. 

grow room fan speed controller

3. Use Neoprene Duct Clamps to Join The Fan and Filter/Silencer

We all know that the high-rpm fan inside is the biggest culprit behind the annoying noise. But there are other sources of it too. One example is the joint between the inline fan and the adjacent filter or duct silencer. The vibration of the fan amplifies even more at this kind of joints.

To overcome the issue, here is what you need to do-

Neoprene Duct Clamps 8 inches

Use a Neoprene Clamp as a joint media in between the fan and filter/silencers. The neoprene suppression inside these products will suppress the vibration and makes sure that the fit is tight. If done properly, that will definitely lower the grow room fan noise by a few decibels.

There are various sizes of them are available such as 4 inches, 8 inches and so on.

4. Do Insulating Ducting

If you have a grow space running on, you must have a duct system installed. But in case it’s a metal duct, and the inline fans are occupied with it, that’s a significant reason behind the noise. Solution?

Well, insulated ducting like fiberglass insulation is a great compromise. The noise can be greatly minimized and it will add a great ‘stealth factor’ to the grow room as well.

Bonus Benefit: An insulated ducting will also run it cooler. Therefore, both the intake and exhaust fan won’t be affected by the hot temperature inside the grow room.

5. Get A Duct/Vent Muffler

Moments before, we’ve talked about insulated ducting, which has a decent efficiency when it comes to quieting inline fans. But using an entire ‘Inline fan duct muffler’ is an advanced version of that, which comes with way more effective in the job.

Duct muffler can reduce the noise up to 25 dB. If you add aluminum ducting with it, the reduction is even more, specially in the bending areas of the duct.

Now, you can either buy a ready-made duct muffler from stores or can make it yourself at home. We’ve noted down the complete instructions to make a DIY duct muffler below-

Steps to Make A DIY Garbage Can Muffler

Bless yourself, you’re going to make a complete homemade fan silencer for your inline fans with the following steps below. Before that, collect these few items-

Items You’ll Need

  • A garbage can of approx. 200+L.
  • Chicken wire or hex netting.
  • Insulation media(Quilt or fiberglass).
  • Silicon gun and duct tape.

Once you have the items in hand, let’s begin with the steps-

Step 1: Measure Your Duct Tube
Check the diameter of the intake/exhaust tube of the duct tube connected with inline fans.  

Step 2: Make A Wire Mesh
At this point, you need to make a wire mesh tube which is of the exact diameter of your exhaust tube, and the length is slightly bigger than the garbage can.

Step 3: Cut The garbage Can and Feed the Mesh Into It
Making sure that the garbage can is hollow enough to feed the wire mesh into it, create two openings on the lid and in the bottom. Once done, feed the wire mesh into the can. If there are any sharp edges around the can holes, you can use tape to smoothen them up.

Step 4: Fix The Wire Mesh Into The Can
Now, fix the position of the wire tube inside the can by applying silica or duct tape.

Step 5: Fill In The Mesh Blanks with Insulations
You should have had either fiberglass or quilt batting as an insulation media. At this stage, stuff the insulation media between the wire mesh and can and fill up the spaced beneath the mesh. The stuffing should neither be too tight nor too loose.

Step 6: Air Tight The Muffler
Seal the insulation opening at both sides of the muffler with silicon and duct tape. Make sure that the whole muffler is air-tight.

Step 7: Place the Duct and Connect The Inline Fan Exhaust
We’re almost done. Now, take the duct and place it in between the muffler carefully. And once done, connect the exhaust of the inline fan with the duct.

As you’re done with the all the steps, here is how it will look-

DIY Garbage Can Muffler

Image Source:

6. Soundproof The Room

If it still seems tough to deal with noisy inline fans,  you can try to soundproof the whole room instead. It may sound complex, but you can do that without major structural reworking at all.

Hanging up several vinyl curtains is a great way to do the job. If you want it to be even more sound and vibration proof, you can stronger sound-damping materials like rubber.

Once again, this is not a direct solution on how to silence grow room fan. It’s just an alternative way to get rid of the noise.

7. Use Duct Silencers

You’ve may hear it many times that duct silencers are the best kind of tool that helps you reducing inline or grow room extractor fan noise. Well, that’s almost correct. Apart from a few drawbacks, this is the best way to reduce inline fan noise.

Here is a good one from Hon&Gun.

8. Use Ducts With Holes in Them

The title of this section may lead you to raise an eyebrow. But trust me, it works. Let me explain-

Ducts, no matter it’s insulated or not, carry on the same noise that’s produced at the opening of inline fans. But if replace with ducts with tiny holes in it, the sound levels fall down to 15-20 dB. The holes on the duct let the sound waves escape and therefore, it acts as a muffler. It’s definitely a quick and effective solution of the problem we’re dealing with right now.

One question that might pop up in your mind is, the holes may slower the air flow(cfm) down. Well, theoretically such tiny holes should not have any chance to stand on the way of the air flow, but in practice, it does affect a little bit. But the impact is so insignificant that you can almost ignore it.

Some Quick Tips

1. Don’t mount the fan directly to the stud. This will damage the stud because of the spontaneous vibration from the fan. Use a rope ratchet, strap or chain that’s hung from the stud with an eye hook. Such systems will let the vibration diminish throughout the ratchet/strap/chain.

N.B: We have a complete guide on how to hang grow lights from the ceiling. You may use the same technique for fans as well.

2. A part of the noise that inline fans produce, propagates through the ducts. If you want the noise canceling efficiency to be even better, isolate the ducts as well. You can use simple wooden/cardboard boxes as like as we explained before.

3. Try running the ducts as short and straight as possible. Because, the more length and bends the duct system will adapt, the more powerful fan you’ve to occupy. This reduces the efficiency of the fans by a lot. Besides, the more powerful fan comes with more noise, obviously.

John Terry

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