Monday, December 4, 2023

RV Electricity â€“ ABCs of generator noise

Dear Mike,
I really learned a lot from your RV Electricity article on generators last Sunday. But do you have a more basic version of it without all the math, sort of like generator noise pollution for dummies?Â â€”Lost in the numbers

Dear Lost,
All right, so here is the Cliff Notes version of Part I on Generator Noise Pollution without all the calculations. For those of you who want to see the mathematics behind it all, the full article is HERE. And no, the math isn’t terrible, but you may get a headache at first learning about logarithmic scales. However, no pain, no gain, right?

We measure loudness of objects with something called an SPL meter, which stands for Sound Pressure Level. And that measurement is made in a unit called a dB or decibel. The more decibels (dBs) you read on an SPL meter, the louder it is. Just know that a 50 dB generator is really quiet, one that’s 60 dB is starting to get loud, and a 70 dB generator is obnoxiously loud if you’re in a quiet area to begin with. So a generator in the low 50 dB range is hardly noticeable, while one in the upper 60 dB range can be heard from many hundreds of feet away. Just in case you have an SPL meter to try out, all generator SPL measurements are taken from 7 meters (23 feet) away using the A-Scale. (Read about SPL meter scales in my full article with the mathÂ â€“ sorry.)

Here’s a video I made comparing the noise levels of two generators. The first one is a Honda EU3000iS inverter generator running around 52 dB SPL, and the second one is a basic 3,600-watt contractor generator making around 68 dB of noise. As you can plainly hear, the Honda generator is barely noticeable, but the contractor generator is really obnoxious.Â  Would you want that running anywhere near you in a campground? I didn’t think so….

There are two big reasons for the sound level differences. First of all, the contractor generator has the gasoline engine out in the open without any noise dampening around it. And it also has a cheap/noisy muffler that makes a lot of exhaust noise. Plus, it’s an AC generator, which means the gas (or propane) engine has to run at full speed all the time, even when the generator only needs to supply a few watts.

On the other hand, inverter generators from Honda, Yamaha and others are built with a lot of sound-dampening material around them. That kills much of the sound of the moving parts. Plus, they have really well-designed mufflers to dampen the sound from the exhaust. Finally, inverter generators really should be called “alternators” because they don’t make AC voltage directly. They really “generate” around 12-volts DC which is then stepped up to 120-volts AC by an inverter, just like you might have in your RV to make 120-volts AC from your house batteries. That allows them to throttle down to a slow idle when the generator doesn’t need to produce full power. And that not only reduces the noise level, that’s also why they’re easier on fuel than a contractor generator that needs to keep the engine running at a full 3,600 RPM all the time.

So are inverter generators worth the extra 200% to 400% price compared to a contractor generator? Well, I take noise pollution seriously, so if you plan to run your portable generator in any kind of campground or park I really feel you should be using a quiet inverter generator with a low 52 dB sound level, and not an open-frame contractor generator that makes maybe 68 dB of sound level (noise).Â  I don’t think that open-frame contractor generators belong in any campground setting.

What do you think? Please comment below, but be civil about it. This is not a flame war, just an intelligent discussion.

Letâ€™s play safe out thereâ€¦.

Mike Sokol is an electrical and professional sound expert with 40+ years in the industry. Visit NoShockZone.orgÂ for more electrical safety tips. His excellent bookÂ RV Electrical SafetyÂ is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert,Â click here.

##RVT852

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Ace (@guest_136106)
2 years ago

I appreciate your article. I have been looking at generators and there is such a huge price difference that I was tempted to get one of the open frame models. However, Now I believe I will just keep focused on the Inverter type. Thanks.

Rob (@guest_47249)
4 years ago

Hey Mike, after owning the Honda 2000 for over 5 years and having no issue’s with it I seen an ad for a Canadian equivalent predetor 3500 inverter sold at Princess Auto. I sold my used Honda for \$650 and bought the Predator for about \$650 on sale. When you look inside the Predator it looks very similar to the Honda, its a little larger and heavier but I would say almost as quiet and after using it for 3 years now without any issues it’s a good lower priced model than spending the almost \$2600 Canadian to purchase the Honda 3000i. I realize I might not get 10 years out of it like maybe the Honda might last but I maintain it well so even if I get 5 to 7 years I have saved large.

Richard (@guest_27357)
5 years ago

Mike, seems like diesel class A’s have variable speed generators which can be quieter than the gas class A’s which seems to run on one speed all out whether you have one a/c on or two or none. What exactly is the difference between these generators and why can’t the gas generators be variable speed?

Mark D. Hunsberger (@guest_27877)
5 years ago

Does it make a difference in sound volume if the generator is fueled by explosive Propane or gasoline instead of much safer non-explosive Diesel fuel?

Roy Ellithorpe (@guest_27352)
5 years ago

Hi Mike, sorry to go off topic, but I don’t know how else to connect with you.
I have a Travel Supreme with 2 Magnum 2000 inverter/chargers. First 1 stopped charging from the generator, then the other. They both still charge fine with shore power. I spent a couple of hundred dollars at my favorite auto electric shop and another \$300 at an RV repair shop. Any advice would be appreciated.
Thanks
Roy Ellithorpe

Chuck D (@guest_27286)
5 years ago

Yes Mike, the ones in Class A and Class C’s. They usually range from 3k to 5.5 K Watts. And regardless of the owners opinion, they are not super quiet.

John Jung (@guest_27244)
5 years ago

I am confused when you say you are making a comparison of generators (or anything for that matter) and then say you are adjusting something. Maybe it’s just me, but a comparison should be the raw comparison of the two items. What am I missing here?

Wolfe (@guest_27188)
5 years ago

Holy “Poop,” Mike… is THAT what most people think an open-frame genny *normally* sounds like? That’s pretty close to what my (~~70db?) LOUD 7500W (I/C, not RV) contractor genny sounds like, but seems much louder than 4KW “yellow” RV genny.

I may not sit on my 4KW as a bench while comfortably talking, but I can talk beside it without shouting… Out at the end of the RV’s normal cord, it’s quite reasonable to talk, and opposite RV side or if I use my extension cord, then it’s “easy to ignore.” My wife who watches TV at “whisper level” says “can tell it’s running, but nowhere near as loud as the [MS] video’s levels.”

Now I’m curious to try my own SPL measures with each of my gennies to see if I’m more deaf than I think or my cheapie genny is really that unusual. :-S

ChuckD (@guest_27149)
5 years ago

Mike I do enjoy your articles even about the portable generators but are you going to cover the generators a lot of RVs have. I don’t think I have seen an RV without one.
Thanks

Mike Roberts (@guest_27253)
5 years ago

Mike, quite a few 5th wheel trailers are equipped with the Onan generators. Especially high end full time fivers and toy haulers. I have a 33′ fifth wheel (in today’s world a small 5th wheel) and had the option of a built in generator. When a generator is needed we have a Honda 2000 inverter/generator.

Jim Anderson (@guest_27147)
5 years ago

Mike,
Your Cliff notes version is Perfect!
And the NPS has these regulations:
Generators must conform to National Park Service regulations pertaining to audio disturbances, which states that “motorized equipment or machinery cannot exceed a noise level of 60 decibels
measured on the A-weighted scale at 50 feet” (36 CFR 2.12).