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Comment by jcims | Hacker News Reader

A commercial delivery drone carrying a six pound package landing on top of a bus between tall buildings is going to make a ridiculous discordant growl. Six of them coming and going within a quarter mile at any given time are going to sound like an auto-tuned pack of hounds from hell.

(This of course is ignoring what happens if something fucks up and suddenly it has 1/8th of a second to decide to fly out of it or brake those giant swinging carbon fiber blades before they encounter human flesh. It's like a trolley problem on a trolley.).

No way. (IMHO of course)

(e.g

Video of a Matrice 600 with a payload of ~8lbs https://www.youtube.com/watch?v=jayVMmvLxOA

Even better, 25 lbs from 60' up lol https://www.youtube.com/watch?v=jULQrdUTngM

)

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Noise levels in cities are already unhealthy. Adding thousands of small rotors is madness.

Using RC helicopters instead of quadrotors would mitigate that a little.

Another mitigation could be to specify allowed jump points (for example on big street crossings where the noise from cars would drown the drones' noise anyway).

I don't think you can "drown out" noise with more noise. It just gets louder overall. (With the exception of active noise cancelling of course.)

Try whispering when someone is shouting :)

If the difference is big enough it's like adding 0.01 to 10. You'd need a lot of drones to influence the total noise level noticeably.

From my experience (Fimi 8 SE ~ 300g drone) the drone is annoyingly loud at < 5meters, and becomes practicaly silent at >50 meters (at least I don't hear it anymore).

Use the mesh which they already need to have to timesync their onboard systems, and have that modulate the rotors according to their ambient awareness. Profit by having an ubiquitous PA booming down from the heavens above...

While true, you can take advantage of the fact the most people don't perceive 2 sources of identical noise as 'twice as loud'. And given the extensive dynamic range of sound it is not uncommon to drown out sound with noise that's a few orders of magnitude louder.

Though I reckon it's more likely that the constant noise of drones will drown out the traffic noise than the other way around. Not just because it's constant but also because it's LOUD.

They aren’t close to identical sounds though. Drones are much higher pitch, and will be clearly distinct.

It’s like when a car honks or someone whistles on the highway. There is a lot of noise, but the higher pitches are distinct.

There's also a psychological effect. What's louder from ten feet away, hair clippers or a hornet?

Well if a sound is loud enough it's going to drown out everything else just by being much much louder. You can't hear a pin drop when lots of people are talking for instance.

That said I estimate a drone to be much louder than regular traffic, at least inside cities.

Yeah... in particular, part of the unworldly annoyance of drones is hearing 4~6 slightly different pitches, all constantly changing, as each prop spins at its own speed to make slight corrections.

You have to consider the car/truck traffic it replaces.

Even my F150 is quieter than these things though, and it can haul way more.

Tell that to the people with Raptors that use Lawrence Expressway as a public drag race track. Half the point of all these race cars is that they're loud as fuck.

Yeah I mean if you throw an aftermarket exhaust on them they can get pretty loud. Mine's just got the stock exhaust on it though. It's pretty tame.

I'd imagine there's some overlap of "people who race cars" and "people with aftermarket exhausts."

The "quieter" part depends on the drone altitude.

It's a lot easier, safer and quieter to replace that traffic with electric vehicles or bicycles.

Even better is if the recipient is the one making the last mile trek on that bike. The logistics of delivering to a hub vs to a hub then also your individual door for that one box of post it notes are so much better for the environment.

I'm quietly hoping and waiting for online stores to take over empty store fronts for last mile delivery. Would love to be able to walk a block away, get my Amazon order, and return it there.

Now imagine that instead of returning something back to a central warehouse, Amazon could have the next customer pick it up or ship it nearby.

Hopefully boxes would not be needed for most of this, too. And any online store(s) could do this.

That would be great, and it's probably coming.

But I would also love if they could drone the package over to my roof if I wanted to.

Where I live, there are few things more dangerous than bicycling.

It's also something only the fitter half of the population can realistically do.

I am. You need fewer trucks than drones to move a given quantity of cargo.

It wouldn't take trucks off the road, it would just increase the capacity that we can transport.

The camera is within 3 feet of that thing and it’s what 75 DB? Compared to the normal city traffic that relatively quiet as it’s horns, squealing breaks, backup beeper etc that are really annoying. On top of this, they are not going to spend very long at street level. IMO, the only real noise issue is raising the street level sounds to higher floors. That’s likely to get serious opposition in many cities.

The critical issues of safety etc seem like a much bigger deal to me.

This report puts it at 66db at 25m away (20m up, 15m lateral)

https://www.hollyspringsnc.us/DocumentCenter/View/23698/Soun...

So say 4m overhead 3m away (5m distance) you have ~80db

https://www.omnicalculator.com/physics/distance-attenuation

Add in the fact that you would feel the prop wash from it and it's going to be a fairly disturbing experience.

Is anyone working on solving the noise problem with drones? Is it even really solvable in any realistic way? What would it take to have a "silent" drone?

Lots can be done, but at the expense of fuel efficiency.

Which is much less of a problem when you can charge the drones from a carrier.

Our drones need a blimp mode : ) :)

A lighter than air mothership makes a lot of sense. You could have the delivery drones glide to the location, fire up the propellers for the controlled package dropoff, then fly back.

Kids with airsoft guns will have a field day

Blimps aren't normally brought down by a few bullet holes. The pressure inside is close to atmospheric pressure, so helium leaks out very slowly.

I have often wondered if larger, shrouded, multi-bladed rotors that can spin at a much lower speed can work. Perhaps uneven blade spacing — or even articulated blades with tunable lead-lag hinges to modulate blade spacing — to spread the noise over a greater frequency range.

Complex problem for sure.

> tunable lead-lag hinges

See, drones traded moving parts for the annoying whiny motors(but fixed in a rigid frame). If we are going to use moving parts anyway, there's helicopters.

First-hand experience: helicopters are wildly more difficult to fly.

Perhaps the lead-lag hinges can be elastomeric and one could purchase props with different fixed hinge stiffnesses for different amounts of noise dampening or frequency spread but perhaps at the cost of prop-speed change response? There'd probably have to be some compensatory mechanism in the flight- or motor-control software that'd be set for a given prop's hinge elasticity.

Of course, I am just idly speculating here on whether there's any benefit at all to any of my blather.

Qualitative opinion as someone who flies drones for fun and profit: yeah, drones, specially the bigger ones (e.g., M600), can be really loud. Once they get above a certain altitude you won't notice the noise, specially in a crowded urban setting, but in quieter residential areas I could see this being an issue. As others said there are ways to mitigate the noise, but at the cost of efficiency.

> those giant swinging carbon fiber blades before they encounter human flesh

Rotor guards exist. They reduce efficiency, but if this is a major concern, it can be done.

Not much can be done today about the noise, short of not using drones and switching to helicopters, with larger, but slower moving blades (more difficult to guard them too).

Am I correct to assume that most of the noise is coming from there being an increased amount of air turbulence coming off the prop blades than their would be were the drone (and thus it's props) less heavily loaded?

Small and light drones are still very noisy. It is not as bad when it's in a steady state, but any maneuvering increases noise by a lot. We have replaced moving parts (as in helicopter swashplates) with fixed, but quick to react motors, spinning at a very high speed. Those generate lots of turbulence whenever they need to shift speeds for maneuvers.

There's someone in this thread saying that their F150 is less noisy than a drone. That is unlikely to be true, but the emitted frequencies are very different. A high pitch whine is, for whatever reason, very noticeable, compared to a lower pitch of similar amplitude. Think dentist drills.

I'm 300 feet from the street in my apartment and I can hear the buses putter along the road and board at the stop, car horns, backup beeping, truck hydraulic brakes, and heavy construction. I don't think an RC drone that sounds like a case fan is going to add much to the cacophony.

Except an RC drone doesn't sound anything like a case fan. It sounds like a swarm of hornets. Maybe that's why it is such a grating sound to human ears.

I think it would make sense for prescription drugs and food delivery.

They gave that drone a chainsaw. What were they thinking??

They were thinking the same thing that someone who put a knife on a Roomba was thinking: "This is gonna be cool."

> Even better, 25 lbs from 60' up lol

Oddly terrifying. Could be a trailer to a new horror film - The Drone Chainsaw Massacres.

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