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Discussion Starter · #1 · (Edited)
One of the things many people mention about the Brutus is that it is loud, especially with a full cab.

I took several measurements of my 2014 Bobcat 3650 with Yanmar diesel today with a Pyle PSPL03, and inside the cab, and results varied from 80-90 dB SPL. With both doors fully open, the average dropped by perhaps two decibels, if that. While the character of the sound changed slightly when PTO (snowblower) was in use, decibels (as measured inside the cab) were about the same for a given RPM with or without the PTO.

Outside of the cab, the loudest readings (anywhere a person would be likely to sit or stand) was in the lift bed, at 95dB SPL.

For comparison, I was using my 12A electric leaf blower to clean the snowblower, and at full blast, the leaf blower measured a constant 92 dB SPL.

With extended exposure, noises that reach a decibel level of 85 can cause permanent damage over time. General consensus is that at 91 decibels, your ears can tolerate up to two hours of exposure without immediate permanent damage.

If you don't want to wear ear muffs, just a tight fitting set of in-ear headphones can give a passive NRR of +20dba, and active-noise cancellation can give you another 20.
 

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I suppose that we should indicate some parameters. So, to start off, how about the following:

1. Model
2. Year
3. Engine (we can figure it out, but seeing it written makes for quicker comparisons/evals)
4. Mods to engine? (timing has an effect on sound/noise; and, well, if you've got a turbo note it [we won't tell anyone]!)
5 Fuel type - fuel type will effect timing (ULSD; biodiesel [tends to retard timing, which quiets things down])
6. Fuel additives? (see comment under "Fuel type")
7. Full or partial cab?
8. List interior changes (I'd solicit for those that one "thinks" could have an effect, but better to just solicit for all changes)
9. List exterior changes

Take readings from the driver's seat, at idle and then at 3,600 rpm (is this max?). I'd figure stationary, as ground surface and other things would tend to over-complicate things for comparative purposes.
 

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I'll measure mine if I can get my hands on a meter.

A turbo does quiet the exhaust, but I don't think the noise inside the cab is exhaust noise. It's a combination of mechanical noise from the engine and hydraulic noise from the transmission. I have a turbo on mine. I'm sure it quieted the exhaust, but I don't think it made any difference in noise level at the driver's seat.
 

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OK, just got my Brutus today. This thing IS LOUD! Holy smokes! How in the heck could anyone let something like this roll off a factory floor? (might be one of the big reasons they didn't sell very well) I'll have to check my tractor, but I'm pretty sure that it's MUCH quieter. Anyway, here's my data:

Model: BRUTUS HD
Year: 2013
Engine: Yanmar
Mods: Stock
Fuel: ULSD (assume- that's what it was shipped with)
Fuel additives: none
Cab: Partial, top with front and rear windows
Interior mods: none/stock
Exterior mods: none/stock

Decibel Readings (taken with Radio Shack Sound Level Meter
Idle (1500 rpm- why this high or idle?): 95
3300 rpm: 105

Kevin, what noise canceling head phones are you using?
 

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Discussion Starter · #7 ·
I use the QC20 to make the engine noise bearable

Cab: Partial, top with front and rear windows
Decibel Readings (taken with Radio Shack Sound Level Meter
Idle (1500 rpm- why this high or idle?): 95
3300 rpm: 105
Wow, that is LOUD. :eek:
Kevin, what noise canceling head phones are you using?
I currently have the $299 Bose QuietComfort 20, an in-ear active cancellation headset, the second highest rated in-ear headphones for cancelling engine noise (best being the SE535). I originally purchased them because I was taking a lot of flights on smaller airplanes (turboprop, etc). The QC20 can plug into your phone for music or as a hands-free headset, and charge off USB.

My original choice, and hunting season standard, are the $25 Caldwell "Low Profile E-Max", these are over-the ear muffs with audio amplifiers (not noise cancelling), and a audio input jack for music.
 

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OK, just got my Brutus today. This thing IS LOUD! Holy smokes! How in the heck could anyone let something like this roll off a factory floor? (might be one of the big reasons they didn't sell very well) I'll have to check my tractor, but I'm pretty sure that it's MUCH quieter. Anyway, here's my data:

Model: BRUTUS HD
Year: 2013
Engine: Yanmar
Mods: Stock
Fuel: ULSD (assume- that's what it was shipped with)
Fuel additives: none
Cab: Partial, top with front and rear windows
Interior mods: none/stock
Exterior mods: none/stock

Decibel Readings (taken with Radio Shack Sound Level Meter
Idle (1500 rpm- why this high or idle?): 95
3300 rpm: 105

Kevin, what noise canceling head phones are you using?
I have no doubt my JD 4120 is louder, I never operate it without ear plugs. Same goes for the little 355 lawnmower. I've never felt the need for earplugs in the Brutus, so it must be considerably quieter.
 

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Discussion Starter · #9 ·
With my factory hard cab, the Brutus is just barely hearing safe.

I have no doubt my JD 4120 is louder, I never operate it without ear plugs. Same goes for the little 355 lawnmower. I've never felt the need for earplugs in the Brutus, so it must be considerably quieter.
I assume you have a full cab on your Brutus? Factory hardtop and doors?
 

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You can decrease the noise by installing flexible foil clad insulation under the seats where there are storage containers leading to the battery and engine....it helped a meaningful amount.
 

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You can decrease the noise by installing flexible foil clad insulation under the seats where there are storage containers leading to the battery and engine....it helped a meaningful amount.
Dan, yeah, will be looking to do that. Those boxes give quite a bit of area to place material in: heck, I might just give a shot at stuffing some blankets in there as a quick test!

Has anyone managed to place any insulated covering on top of the engine (not, as others have done, under the bottom of the box bed)?

I suspect these things, ATVs/UTVs in general, just don't have the mass to absorb the engine sound. These Yanmars are in small excavators, and excavators are a lot quieter: they have a lot of insulation in the engine compartments.

Still goes back to thinking that Polaris and others really ought to publish warnings to wear ear protection.

I wasn't able to physically check one of these things out before purchasing. I could only go by general, non-quantified, comments that these were "loud." I kind of dismissed this as just something normal for diesels.

I suspect that this is going to take a lot of different changes to improve. I'd like to try some 2-stoke oil as fuel additive, figuring that this will reduce a bit of IP and injector noise.

Any chance that these things might quiet down a bit after they start to break-in? Mine's got like 10 hours on it.

Before I try anything I'll take some more readings just to make sure I'm getting consistency here.

Also, my idle is something like 1,380 rpm, which, from a quick search (too lazy to pick through the service manual:eek:) shows it's supposed to be around 1,250 rpm (why so high? all my diesels tend to idle around 900 to 1,000 rpm).

I also suspect that my control lever isn't adjusted properly (despite the assurances from the dealer that it was- I'm hoping that it has the newer control lever). Seems like I have to get the rpms up quite a ways before it really wants to move: my tractor responds much quicker. I'm thinking that I'm only really able to top out around 24-27 mph, though I've only given it one good run up the road. While a better adjustment here might more often keep me out of a higher rpm range, there's still the issue of that 95 db idle!

Not related, but the other day I switched off the engine while IN gear! Was on fairly level ground and was able to rock the vehicle and get the lever into Park. I'm wondering why there's no lock-out from shutting off the engine until the gear lever is in Park? That shift lever still feels like I'm on the verge of breaking something!
 

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Discussion Starter · #13 ·
Not related, but the other day I switched off the engine while IN gear! Was on fairly level ground and was able to rock the vehicle and get the lever into Park. I'm wondering why there's no lock-out from shutting off the engine until the gear lever is in Park? That shift lever still feels like I'm on the verge of breaking something!
I do this all the time, pretty much leave the shifter in "L" except when I need to stop temporarily on a hillside. >:)

It's a bad habit to get into, but the owner's manual even says you can start the engine in gear, so long as the treadle pedal is in the neutral, center, position.

You can decrease the noise by installing flexible foil clad insulation under the seats where there are storage containers leading to the battery and engine....it helped a meaningful amount.
I've been considering wrapping the outside of the storage boxes in cheap MLV for this purpose. You should start a soundproofing thread in the DIY forum, post pictures!
 

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I assume you have a full cab on your Brutus? Factory hardtop and doors?
2013 Brutus HD
Kolpin poly windshield
Polaris rear glass
Polaris sport roof with headliner
Polaris canvas doors
Carpet and padding on back wall
Lots of mass loaded vynil/foam/foil sound absorber under seats and around engine.

It's still what I would consider loud, but not as load as my tractors.
 

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Polaris sport roof with headliner

Carpet and padding on back wall

Lots of mass loaded vynil/foam/foil sound absorber under seats and around engine.
Is that indoor/outdoor carpeting on the back wall? How was it adhered?

Did you install the material just around those seat buckets? Wondering how much I need to disassemble.

And "around engine," how/where?

Any chance you could share some pictures?

Really would be great to see what kind of numbers you're getting.

A few db makes a big difference. As noted in an earlier posting of mine the Kubota RTV is 89db at max throttle. Comparing against my 105db that would make the Brutus EIGHT times as loud (impact on hearing).

I looked through the Owners Manual and I found no reference or warning about needing to use hearing protection.
 

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On the back wall I used 1/2" automotive carpet padding and non-woven trunk carpet. I removed the panel to install it, it's glued on with spray adhesive. I used a sheet of HDPE to make a panel over the engine. It sits across the frame rails and extends from the back of the cab to the first crossmember and is held in place with a few plastic push pins. The bottom is covered with mass loaded vinyl sound absorber. I also covered the bottom of the bed, front kick panel, center console, drive shaft tunnel, and wherever else possible with the same absorber material. I stuffed some openings in the cab with foam to block drafts and dust from entering the cab, it may also help block noise. In fact the noise reduction kit for the Ranger 900 includes precut foam pieces for this purpose. The headliner almost certainly reduces noise reflecting off the roof.
I did each of these things a bit at a time, and there wasn't any one thing that made a noticeable difference, but I guess all together it does help. It's still a loud machine.
 

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Many thanks for that info! I was especially wanting to hear if folks had been able to get a cover on top of the engine (and you have).

What is the "back panel" and how is it removed?
 

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Discussion Starter · #18 ·
Polaris Engineered Cab Seal Kit (for RANGER XP 900 )

the noise reduction kit for the Ranger 900 includes precut foam pieces for this purpose. The headliner almost certainly reduces noise reflecting off the roof.
I did each of these things a bit at a time, and there wasn't any one thing that made a noticeable difference, but I guess all together it does help. It's still a loud machine.
Is this distinct from the Ranger 900 "Cab Seal" kit?, This Polaris kit video should give some idea for where to install sound blocking material:
 

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How loud is the Brutus, really?

On my 2014 HDPTO I added the foil backed foam to the lower back panel. Behind the. Seat, around the outside body panels and wrapped the storage. Buckets. Under. Both. Seats. I also installed the official. Polaris Brutus very. Expensive. Noise suppression kit that consists of two pieces of thick foam that covers. The front. Of the seat. Base (you have to pull the floor up. To install it) and a formed light grey panel that. Fits behind the seat backs up to the rear. Window. It makes. For a nice finished appearance in the. Cabin and it the whole thing made a noticeable difference in the. Cabin noise. Level.
 

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Just completed a pretty thorough sound suppression project on my 2014 Brutus with full cab/canvas doors. I bought both Polaris upper and lower cab liner kits and in addition I lined every thing I could with rubber/foil liner. It's quite a project as the floor must be taken up to install the lower kit. I also wrapped the tool tubs under the seats with the liner and also the lower rear panel behind the seats. The upper liner kit, while not so involved, was sort of a custom job as none of the mounting holes matched up with any thing. It was as if the hole pattern was misaligned by approx. 1 inch front to back. (Made in China !) I also lined the roof with as much rubber/foil liner as I could. Also had to make an oversized plate to mount the dome light and cover the misaligned hole for it in the liner. It gives the cab a nice finished look. I measured sound levels using an app for my cell phone at an average of 76.2 db at both idle and full throttle sitting with both doors closed. The change in throttle setting only seemed to change the frequency, not the sound level. You could actually have a conversation in the cab. The project cost over $500 and a couple of days time. Was it worth it? I'm happy. It should have been installed when built.
 
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