was posted 3 days ago in /c/Technology, here :
https://lemmy.world/post/15468260
what they did :
“Our product takes in a full blow of air and separates it,” said team member Leen Alfaoury. “Some of that air comes out as it is, and part of it comes out shifted. The combination of these two sections of the air makes the blower less noisy.”
… “It ultimately dampens the sound as it leaves, but it keeps all that force, which is the beauty of it.”
Their design cuts the most shrill and annoying frequencies by about 12 decibels, which all but removes them, making them 94% quieter.
about 12 decibels, which all but removes them, making them 94% quieter.
This “conversion” from decibel to per cent is more than ridiculous.
Why? dB is logarithmic so it’s difficult for people to picture how loud something is, if that’s the only number given.
And so are our ears. That’s why we use db. So 12db is not perceived by us to be 94% quieter.
Well, 93.7% to be more exact. Did you recalculate it yourself the same i did ?
The team reduced the overall leaf blower noise by about two decibels, making the machine sound 37% quieter.
You omitted the most important data, it’s 2db overall, not 12db.
So your own “recalculation” isn’t even in the right ballpark as the correct answer.
Its people that misinterpret the information and perpetuate it like you are doing here that makes these look far better than they actually are.
Your calculation was about energy. But the calculation of energy is next to useless when you are trying to compare two different noises. You need to care about perception.
The perception of noise is quite complicated. But as a rule of thumb: when some noise changes by -10dB, then you hear it about “half as loud”.
Source: I have a university degree in acoustics.
So for the reduction of -12dB here, it will be perceived as “nearly half as loud”. Very different than the “94%” is suggesting.
Just saying it doesn’t decrease the power is a bold claim without providing anything technical to support it.
I’ve read multiple articles and videos and yet this very crucial information is intentionally not included.
The claims are false, you can’t suppress or mute something with a tradeoff, unless they have somehow magically figured out physics anomalies. Would love to see some proof of this claim it doesn’t decrease power output.
Are you saying novel mechanical engineering designs are impossible? That the mechanism of a leaf blower is so near perfection, that a well funded team of 4 mechanical engineering students could not, without VIOLATING THE LAWS OF PHYSICS, have simply found a better mechanism?
I agree with your “show me the numbers” critique, but I find your complete disregard of what may be a better answer without any data at all to be equally foolhardy.
He has a point though… OVERALL noise was only suppressed 2db. It’s only 12db in a specific frequency. EVERY article has more or less ONLY stated the 12db value. It seems more and more these days that you just have to assume that the article headline is at best mostly false, or obscenely misleading.
2db overall… is kind of fucking pointless. I mean… as someone afflicted with hearing problems I know that every db matters. But all this hubbub for something that should just be found, then implemented without all this fanfare… the general public will not care about this, yet I’ve seen 3 articles on it for some reason.
And most normal people don’t understand the logarithmic nature of the db scale anyway. Every 3 db is technically a doubling in power. But it takes 10db for our perception to halve/double.
I am saying every single one of these claims have never wound up being actually true since they go against the very nature of physics. Yet people perpetuate the claims and defend them without the supporting data.
So to not provide the data for one claim, while providing the data for another is only done to mislead from the truth.
Sorry for not accepting what they say at face value since it goes against multiple things.
Destructive interference is a thing. The energy of the vibrations doesn’t go away, however you CAN shift that energy into different frequencies and destructive interference done correctly will effectively shift it into so high frequencies that the vibrations are better compared with heat than with sound (what is heat convection anyway if not extremely high frequency sound? :)
Heat is electromagnetic radiation - photons, sound is mechanical displacement - phonons.
They mostly propagate the same due to being waves, in most other respects they are very different.
Heat convection is an entirely separate process where heat radiation is aided by the movement of the surrounding medium. Where it would otherwise heat up it’s environment, convection keeps the environment from heating up. Compare coffee in a thermos (very little convection) to a cup you’re blowing on (significant convection); more air movement - more cooling.
Also, destructive interference does not at all work like that.
Maybe a more useful analogy could be that waves have like walking animations, where in part of the animation they go up, and in another part they go down. Destructive interference happens when a wave in its’ “up” phase crosses a wave in it’s “down”, meaning the resulting movement looks like nothing. The waves don’t however interact in any way, and will continue on their way and on their own animation cycles.
The shifting and heating parts are technically true but require very specific circumstances, enough so that I’m more prone to believe it’s another misunderstanding of the physics behind this. But I’ll give you the benefit of the doubt.
12dB is literally nothing in reduction when the lawn dudes are blasting 60-100db
Decibel scale is logarithmic, which means 10db change is reducing perceived volume by half.
No. It means the sound energy is dropped by half. Our audio perception is also logarithmic however. It’s why we use db.
12 dB is a pretty decent reduction if your goal is hearing protection, 100->88 is also bringing it to something that absolutely needs hearing protection to something that’s borderline acceptable for an 8 hour shift depending on your local laws, mine say 4 hours but still, way more comfortable to use.
The team reduced the overall leaf blower noise by about two decibels, making the machine sound 37% quieter.
It’s an insignificant 2db, I don’t know why buddy didn’t provide the relevant information.
Eh, I’ll take it though. I live in a fairly quiet part of town but the street has gotten pretty busy in the last could of years. And visually, I guess the street seems to open up making drivers get… spicy now and then. The fucking motorcycles, man. These noisy fucking middle-aged infants making 130 decibels while only going 15mph make me see red. I’d gladly take the lawn equipment noise.
Decibels are a logarithmic scale, so it scales exponentially. Because of this, reducing by just ten is actually very significant and would reduce the perceived volume by half, and would reduce the actual sound pressure even more than half.
If it were me that designed this, I would license out the design for manufacturers to use in their production models instead of making some kind of attachment that is unlikely to work on all models. That seems much more likely to achieve the goal of reducing noise from leaf blowers long term. Get like 3 manufacturers on board that could even charge a premium, and you have reduced the noise potentially forever while still making a tidy profit.
MAKE GAS LANDSCAPING TOOLS ILLEGAL
Give away free electric tools if they trade in their gas ones. It’s so bad for health to be huffing 2 stroke fumes all day every day.
Edit, I realize that this is meant for a electric leaf blower since it would do fuck all for a gas one. Doesn’t change my opinion about landscaping tools tho
“Electric leaf blowers are already far quieter than their gas-powered peers, but they still aren’t the kind of thing you’d like to hear first-thing on a Saturday morning. Looking to improve on the situation, a group of students from Johns Hopkins University have successfully designed a 3D printed add-on that manages to significantly reduce the noise generated by a modern electric leaf blower without compromising the amount of air it’s able to move.”
First two sentences of the article.
I don’t know mate, I wouldn’t replace my electric tools–drills, grinders, saw… with gas ones. But these outdoors tools are a different kind of beast. I’ve only used an electric chainsaw and it was an absolute crap, maybe there are better ones but it was crappier than the smallest and shittiest gas chainsaws I’ve used, and a cord around you in that setting isn’t great either.
The problem with electric gardening tools is they aren’t that feasible for contractors.
Batteries don’t last long and take a long time to charge, so it’s just not an option when you’re working all day. Corded means at every location, you have to figure out outlets, extension cords, fuss with tangles and obstructions, etc.
If you’re doing your own lawns, yeah, you can probably get into a workflow that works for you. But a lot of people hire out for landscaping.
Swappable batteries resolve this issue pretty well. The energy density is far from comparable, but if you’re already hauling a van or trailer to the job site, then a dozen spare batteries isn’t an issue.
Gas being a better energy source than batteries in every way except for the health and environmental issues is a real bitch and why this is such a problem. Cords are a hassle and you will need a lot recharging batteries all the time, so you notice the downsides immediately and acutely. These are solvable problems though. Even running an efficient gas generator would be better for the health of landscaping contractors than being around 2 strokes all day.
Look again! I have a dewalt chainsaw, and I love it. I burn about 13 cords of wood each winter as it is our primary heating source. It runs and runs and runs.
I think the key is to keep the chain sharp. I use the timberline sharpener, and it gets the chain razor sharp, which means less stress on the motor and longer battery life.
Electric is so much quieter. They have them in Singapore
The gardener in my last apartment replaced all of his powertools (mower, blower, trimmer, …) with electric ones powered by an accu-pack he carries on his back. This is an absolute game-changer! I could actually sit outside again and even do stuff for work, when he was there.
I still say replace them with rakes.
I get what you’re saying, but leaf blowers are also commonly used for cleaning up extra grass clippings from the roads, etc.
