Why are backpack leaf blowers and lawn mowers so darn loud?

See subject.


I’m not an expert, but IIRC it’s because they generally use 2-stroke engines, which tend to be louder.

Not much room for a muffler, either.

Since good quality mufflers exist, I stay convinced that the main purpose for the noise is proving to neigbors that you are a hard working nut.
There might be noise from the blower assembly too, though the OP included lawnmowers.

So why do they use 2-stroke engines instead of some other, quieter engine design?

IAMNAExpert, but my guess would be:

There are (currently) no laws requiring a noise threshold (unlike cars), so the manufacturers have no incentive to bother.

Consumers use leaf-blowers rarely and will be more likely to put up with the noise or wear protective headphones than spend 100$ more on a more quiet model, so again the manufacturers have no incentive.

Compare lawn-mowers which can also be damn loud, but are used more often and may run contrary ro local noise regulations, and you have many different models, some of which are much more quieter than others.

The best thing IMO would still be to ban the things and sweep the leaves up with broom/fork as previously: saves gasoline, no noise, a bit of physical exertion is good for people (and it’s not as exhausting as snow shoveling) and it’s better for the enviroment (leaf-blowers produce so much wind that the small critters in the soil are harmed).

And they really aren’t quicker than a broom/fork in any discernible way, and carrying that heavy thing on your shoulder is not that much less of an exertion than raking the leaves instead.

Because the alternative is four stroke, basically. Each design has it’s merits and downfalls, making one favourable over the other in most situations.
Two strokes are lighter, simpler and produce more power for their size/weight than a comparable four stroke engine, but they necessarily consume oil, are loud and aren’t terribly efficient.
Four strokes can be made to run pretty quietly, are much easier to set up for efficiency and don’t need oil adding (if it’s in good working order), but have many more moving parts, making them heavier, more expensive to produce and adding complexity. They also only have a power stroke every fourth stroke, (two revolutions of the crankshaft) hence the name ‘four stroke’. Two strokes give a power stroke every other stroke, again, hence the name.
All this means that if you want an efficient, clean, quiet engine for, say, a car or similar, you want four stroke. If you want a compact, cheap, simple engine which doesn’t have to meet emissions or noise requirements, two stroke is the way to go.

Actually I was surprised to learn that 4-stroke engines are pretty common in lawn mowers and even handheld leaf blowers. My WAG was that only a few expensive models would have 4-stroke engines.

Anyways, 4-strokes aren’t inherently quieter than 2-strokes. But you can at least put a muffler on a 4-stroke. Effective mufflers are bulky, heavy, and hot; a significant manufacturing expense; and not something you’d want to carry in addition to everything else.

For the individual who’s buying and operating the equipment, the noise problem is solved with a 10 cent pair of earplugs. The people who are most annoyed by the noise (you and other neighbors) don’t have any say in equipment purchasing.

There are two components to the noise: engine noise and blower noise. And it is pretty easy to hear these components separately to understand just how loud each one is.

I have an electric leaf blower, and even without the gas engine it is pretty darned loud, sort of a turbine wail. I don’t think the electric motor contributes much to this scream.

I also have a few 2-stroke tools from Echo (the people who make those kinds of things): an edger, a string trimmer, and a hedge trimmer. All three of them use the same lightweight gasoline motor and all three of them have the same penetrating staccato note that leaf blowers have.

The gas-powered leaf blower combines the best of both worlds: the loud two-stroke motor with the wailing turbine sound of a serious blower, resulting in maximum annoyance.

4 stroke engines are common is larger sizes like lawn mowers where power is needed i believe. i’ve got a two stroke lawn mower (free for the taking because owner was moving) and it is a little of the top mower, little power compared to any 4 stroke mower i’ve used.

also 4 stroke engines have oil that needs to be circulated and this depends on engine position. 2 stroke engines have the oil mixed in the fuel so they are lubricated in any position they will run in; so small equipment that is placed in many positions while it is running is better 2 stroke.

This sounds like anti-leafblower propaganda.

I don’t think any two-stroke lawn mowers are sold in the U.S. any more. Lawn-Boy was the last brand, I think, and now they’re four-strokes. Another reason small gas engines are so noisy is because they’re air-cooled. They have no water jackets enclosing the cylinder(s).

This is a good point. The guy behind me has a smaller lawn and fewer trees. Yet he spends more time with his banshee than I do with my rake.

Some people need to get a life. I see them all summer after mowing blowing the clippings off the sidewalk. Come on!

Part is economical. but I am afraid part is pschological. It gives some people a sense of power to be using a loud, noisy machine.

As for blower noise, I flipped through some books. Angling the blades one way is more efficient and another way quietier.

To the OP, you skipped vacuum cleaners. I guess there is no end.

At the end of a power stroke in a 2 stroke is exhaust directly exiting and according to a manual of a outboard motor I used to have the exhaust is supersonic, this is sure to be louder then a 4 stroke with it’s own stroke to clear the exhaust.

Generally speaking, two stroke engines are lighter than comparable four stroke engines for a given horsepower output, and they make better use of a given displacement to make that power. Unlike lawnmowers, leaf blowers have to be carried, so weight is much more of a concern. You see the same trend with line trimmers/weed eaters, small scooters, small dirt bikes, etc.

As far as I’m aware, there are no regulations in place restricting sound levels on them, so manufacturers aren’t exactly in a rush to implement sound suppressing equipment.

Many blowers can create winds in excess of 200 mph, so the wind noise and associated turbine will make a lot of noise independent of the engine. Also, keep in mine that the engine will be running at relatively high RPM when the blower is at full throttle; as with all engines, sound will increase as RPMs increase. Blowers aren’t much louder than any other gas powered equipment when they are idling.

Finally, there’s a lot of hate for Lear blowers, but they are used for more than just blowing leaves around. Sand, soil, and other debris routinely cover the driveway, porch, and sidewalks around my property and then gets tracked indoors and a rake isn’t going to get any of that. A 10 minute job with the blower would take many times that with a rake and broom. I don’t deny the laziness on my part, but it’s damned convenient.

:rolleyes: Yeah, those scientists that measured the effects by taking soil samples were only interested in propaganda, as our scientists always do. :smack:

Did those scientists publish their results?

I don’t know. Why, would you believe German scienists? After all, they’re biased and socialist.

You really need to point us to a cite here, Constanze, as I for one have never heard of any studies of this nature. That doesn’t mean they don’t exist, of course.

Roll your eyes all you want, dude, but nowhere in your original post did you mention anything about scientific studies backing up that interesting bit of info you shared. I am happy to read a cite if you have it. However, as much as I’m amused by the idea of bugs, small rodents, or maybe Whos clinging onto blades of grass for dear life or tumbleweeding through their burrows as their leafy canopy is blown into the neighbors yard, it seems more the plot of a Looney Tunes cartoon than based in reality.:stuck_out_tongue:

Now, if by “critters” you mean microscopic organisms, then maybe there is something to it, but still, color me skeptical that the “harm” is really enough to impact the environment in a substantial way.