How loud are robots and motors compared to animals ?

Thread Starter

DarthVolta

Joined Jan 27, 2015
456
Like if a cat runs down the road, or a mouse , or a bird flies by, they could be pretty quiet, but still go fast. What's the best (publicly) that humans can do, to make fast mobil robots, but that are also quiet ? For that matter how loud is a Tesla, if it's not pushing air.

What about motors in general, like how quiet can they make RC cars these days ? I can easily hear an electric 1 of them drive down the street, but I'd never hear a cat run down the street.
 

Thread Starter

DarthVolta

Joined Jan 27, 2015
456
So what's the state of the art, publicly, in quiet motors for small robotics?
Maybe I watched this episode too much
https://www.vidio.com/watch/260141-the-x-files-season-3-episode-12

A small town is plagued by deaths in which the bodies are found covered in cockroaches. Working from home, Scully has scientific explanations for all of them but Mulder—at the crime scene with an attractive bug expert—suspects the insects may not be organic, or earthly
 

jpanhalt

Joined Jan 18, 2008
9,451
Tesla's are pretty quite. But there is some noise. The first one I saw up close was a bit eerie. Go for a ride in a sailplane. They are quite quiet after release from the towplane.

It's the bear you don't hear that you need to worry about.
 

wayneh

Joined Sep 9, 2010
16,390
I suppose a balloon floating with the breeze must be darn near silent. They need to fire the burners once in a while, so maybe it's not fair to listen only to the floating phase.

If your metric is decibels per pound mile, I think a man on a bicycle would be tough to beat. One with a fairing might be even quieter.
 

SamR

Joined Mar 19, 2019
2,134
The idea is to make it supersonic. That way it hits you before you hear it. Well offshore one day we heard what sounded like distant cannon fire. It kept on for a while and I finally figured out that it as an aircraft carrier well over the horizon launching planes. The booming was as they went supersonic. A bit later we could hear them screaming overhead but never did see one.
 
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MrAl

Joined Jun 17, 2014
7,604
Interesting question.
Some of those computer fan motors are very quiet, the low rpm ones, while the high rpm ones are very very loud.
I think the gears in some devices make most of the noise, or the fan blades to cool the motor.
The magnetic forces are very soft it is the mechanical mechanisms associated with the forces that make the noise.
Even using dampered bearings helps reduce noise.
 
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jpanhalt

Joined Jan 18, 2008
9,451
Not surprised the Chevy sounds like my home phone or a squeak. ;) Wonder whether it is loud enough to be heard over the cell phone held to the person's ear?
 

visionofast

Joined Oct 17, 2018
70
there're articles and books about artificial muscle and electroactive materials,
indeed, these polymere materials are supposed to get close to natural muscle by aspects of speed,hysteresis,strenght, etc.
even they calculate fatigue for them based on hysteresis effect.
 

SamR

Joined Mar 19, 2019
2,134
There is quite a bit of research being done on acoustic noise cancelation and suppression. Started with improving on headsets. First to stop loud outside noise but still allow for quiet conversations to he heard while wearing headsets that provide hearing protection. Then to backfill outside noise to baffle it and not interfere with hearing what signal is being transmitted by the headset speakers. Not to silence an outside object's noise but to make it seem to be silent so as not to interfere with more important sounds. Still a lot of work to be done on noise cancellation by backfill.
 
Reduction gears probably contribute more noise than the motors themselves. Motor whine might be contained with shock mounts and couplers, or maybe by controllers that run at inaudible frequencies. With fans, the fan blades moving past a grille or fins can create a tone much as a mechanical siren does. That would apply to tires and wheels: avoid big lugs and wheel fins that disturb the air.
As for cats... I know a small house cat that sounds like a small elephant when she runs upstairs.
 

MisterBill2

Joined Jan 23, 2018
6,107
How quiet are motors? That is a very broad question. I can not hear the motor in my dishwasher, but I can not hear over the motor in my cheap air compressor. Industrial robots are quiet enough to be dangerous when they move fast, and they do not interfere with nearby conversations. RC cars will not be able to sneak up on a cat or dog under normal conditions, and at high speed they do make a bit of noise.
But then you see a show with robotic animals spying on nature and it is clear that some systems can be very quiet.
 
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