I can't comment on any particular component other than the ones I own. I can answer generically.

A silencer located between the hood and the exhaust fan will reduce some fan noise, mostly high frequency blade tip turbulence noise. It will also attenuate high frequency duct noise generated on the fan side of the silencer.

It won't affect noise generated in the hood, or in transitions between the silencer and the hood. If there is room for a silencer, an in-line fan will not preclude the use of one.

Noise in hoods with remote fans should be mostly hiss from air passing through the baffles or meshes.

Changing duct size, fan, and hood at the same time eliminates any chance of estimating whether your noise will go up or down. 1100 cfm through a 10-inch duct should not be annoyingly noisy, so the question is: Is the fan large enough to pull that airflow rate without generating a lot of blade tip turbulence. If not, then a silencer should help, but the result would be hard to predict.

If the fan is in the hood then there is little point in using a silencer, and the primary source of noise will be close to the cook and potentially annoying.

kas

Thanks, Kas, for taking the time to explain about the silencer. This is helpful.

We have an attic mounted Fantech FKD 10XL, about 1250 cfm, with the LD10 silencer. We run 10'' ductwork from the hood, although at one point we transition to a rectangular 14 x 5'' duct to get it through a wall. At full speed, it is extremely quiet. As kas has noted, the only noise is the actual airflow through the hood baffles (a 64'' Modern Aire liner). There is no fan motor sound at all. Since I have never run the system without the silencer in place I can't swear to what it is doing, but the absence of motor noise is great and the cost of the silencer was trivial, so I'd certainly recommend it.

Not sure why your current setup is so noisy. Can you tell what you're hearing? Is it airflow through the hood, motor noise, fan blade turbulence? What kind of hood filtering are you using? The baffles in our hood are preferred compared to mesh filters I suspect from a noise standpoint. Oh, and since you asked, they are super easy to clear: just pop them out and throw them in the dishwasher. Nothing could be easier. I love the Modern Aire hood, cannot imagine a better product and would certainly suggest you look at them (www.modernaire.com).

I have a sililar setup to clinresga, although all my ducting is 10" round (out of hood w/ a 45 deg elbow, 2' straight to LD10 silencer, 1' straight to 45 deg elbow, 10" shanty cap vent w/ some chicken wire to keep chickens out). With the mesh filters in place it whistles. Without the filters it just makes a low rushing noise.

Thanks so much for the responses.

Clinresga, answers to your questions below:

Can you tell what you're hearing? Is it airflow through the hood, motor noise, fan blade turbulence?

When I first start it up, there's a humming noise, sounds to my untrained ears like a motor of some kind. Then, it's maybe is just a very loud rush of air along with what still sounds to me like a motor.

What kind of hood filtering are you using?

I have a FanTech with mesh. Not sure if the mesh is the reason for the noise, but It's a nightmare to clean. Also, my fan is just 550 CFM and I cook fish in a hot cast iron pan regularly, so I need to run it on high. Hoping increasing the CFM to 1100-ish will allow me to run on medium...

One thing that seems to be shown here, from your experience and also laranbrian's, is that mesh filters are noisier. We have "pro style" metal baffles. Here's the (obviously biased, but I think informative) quote off the Modernaire site:

"Modern-Aire Ventilating believes like most major range manufacturers and restaurant supply houses that the most efficient filtration system is the Baffle Filter. Unlike non-filtered range hoods, a Baffle Filter catches up to 97% of all grease and grease particles before they ever enter the interior of the range hood, making clean up a breeze. Unlike mesh filters, the air passing through a Baffle Filter is not restricted, thus allowing a smoother and quieter transition. Perhaps the most important aspect of the Baffle Filter is that the baffles in the filter are positioned to eliminate direct passage of flame through the filter thus making it one of the safest and most efficient filtration systems available today."

I think it's a far superior design for the liner. And it looks cooler too :-)

Based on particulate size distribution collection data for commercial baffle filters that I have seen on-line, I wonder about the 97 percent assertion. It is true that the finer particulates that baffles only partially collect represent proportionately less grease by weight than larger particulates, but can these represent only 3% for varied types of cooking? I think the operative clue here is the "up to" choice of wording.

Otherwise, I believe Modern-Aire has nicely summarized the advantages of baffle filters.

kas

These responses are really much appreciated. In going to look into Modern-Air today.

Clinresga and Kas- Do you happen to have any head to head experience with MA vs Broan (baffled) as far as loudness? Also, any particular MA power pack you think I shoul look at?

I have a baffled Wolf Island Pro (built by Independent) to Fantech silencer to Wolf (built by Broan/NuTone) "1500 cfm" roof-mounted radial fan via a ten-inch duct. At full speed one can carry on a normal conversation around the cooktop, but the sound level is noticeable.

Along with the air noises there is a slight rumble. I suspect imperfect balancing of the fan blade assembly, but I haven't tried to get it balanced yet.

I have no other personal relevant experience with MA or Broan.

kas

As you know the only personal comparison I can vouch for is between our MA hood and our VAH at the lake house. With some embarrassment, I'll post the link to a thread from the old days when we were deep in the throes of our remodel which attempted to quantify the noise levels:

Vent Hoods and Noise, the real story

I can't comment about a Broan. Both kas and I use similar blower setups, ours with the fantech silencer and a fantech attic mounted 1250 cfm blower.

Thanks so much everyone.

Clinresga: since my house is set up for an online blower in the attic, I thinking just going to profit from your research and experience, and get the exact same setup that you have.

Don't be embarrassed, I'm sure many people have appreciated re decibel measurement info :)

So, you have a e have an attic mounted Fantech FKD 10XL, about 1250 cfm, with the LD10 silencer, and a 64'' Modern Aire liner with pro style baffles.

Would you be able to tell me the model of your MA 64"?

Also, is it the type of inline blower that connects right into the ductwork, or the kind I've heard about (but don't really understand) that's referred to as "inline" but actually sits in the attic, in it's own separate box with the squirrel cage and motor separated from the duct?

Our MA is a liner--it sits inside a custom cabinetry alcove, so all it consists of is the SS "box" with the baffles inside. It is hidden within the cabinetry. It's a custom order: you just contact MA, give them the exact specs (which was great for us--we got exactly the right width, was able to add a bit more to the depth, and was able to position the duct collar exactly where the ductwork emerged from the ceiling). They are great to work with, particularly if you live in a state that has no local distributor, as then you can work directly with the factory which was super easy.

The FKD 10XL is an inline blower. It looks like a squat cylinder and mounts (not surprisingly!) in line with your ductwork. Here's a picture:

Not exactly sure what your question is: it does sit in the attic, it's a self-contained unit that mounts via a spring loaded clamp system to a nearby stud. Fantech's website is useful and they too are easy to deal with by phone if you have any questions.

Emailed you, clin. Thanks again.

Fantech blowers that I've investigated are axial fans with the direct drive motor inside the fan blade circle (like a very compact ceiling fan). Typical commercial upblast fans mounted on restaurant roofs usually have an offset motor driven fan in which the connection is by fan belt.

kas

Thanks, Kas ;)