Drone Noise – Is it a Problem?

As more and more people buy drones for personal use and more businesses look to use unmanned aircraft will the droning buzz of drones become a problem?

Just before the last drone industry networking event, I organised for the Civic Drone Centre. This tweet from UCLan’s research Twitter account received the following reply:

Tweet

This got me thinking. Are UAVs too loud? Is drone noise a problem? I don’t think it is and that it will be less of a problem.

I don’t think it is, and that it will be less of a problem in the future.

Drone Noise

First, we need to talk bout noise and how we measure it first. Noise is typically measured in decibels (dB). Without going into too much detail, a decibels is a ratio based on the sound pressure threshold of the human ear.

Human Perception of Sound

Then there is a human element. Everybody is different. A person’s ‘threshold’ may be different from the one used in the calculations.

Also, an individual has certain preferences for certain sounds.  Think about music. I’m sure there is a type of music you like that someone else will hate, and another who does not hate or like it. This is similar for the noises drones make. Now, I have not met a person who loves the sound a quadcopter makes. However, I do know people with differing opinions on how much drone noise bothers them.

Finally, we also have to consider the noise in the environment we hear it. We have the phrase ‘quiet enough to hear a pin drop’. So if the otherwise quiet countryside a drone is going to be an unwelcome noise.

What the Drone Regulations say?

Currently, in the UK there are not specific regulations for drones to be a certain noise. However, regulations around machinery may apply to them.

But, the European Aviation Safty Agency have draft drone regulations under review. These do mention maximum noise limits for some classes of drones. They set the noise level at 80 dB at 3 meters.

What does 80 dB sound like?  This noise comparison chart relates some decibel readings to real world examples. I have pulled out what the comparable sounds are for 60 dB to 100 dB:

  • 60 dB – conversational speech or an air conditioner.
  • 70 dB – shower or dishwasher.
  • 75 dB – toilet flushing or vacuum cleaner.
  • 80 dB – alarm clock or garbage disposal.
  • 85 dB – passing diesel truck or snow blower.
  • 90 dB – squeeze toy or lawn mower or an arc welder.
  • 95 dB – inside subway car or a food processor or a belt sander.
  • 100 dB – motorcycle or a handheld drill.

So the maximum decibel level allowed for drones is less than a diesel truck. Also, most of the time you are not within 3 meters of a drone. However, on a quiet walk in a remote forest, a drone may still be disturbing.

Drone Design

I checked on of the books I have designing drones – [amazon_textlink asin=’1600868436′ text=’Designing Unmanned Aircraft Systems: A Comprehensive Approach’ template=’ProductLink’ store=’atmosblog-21′ marketplace=’UK’ link_id=’bad9d62f-5f75-11e7-9d85-834f4c4f8268′] by Jay Gundlach. It does have a short section on acoustics. Although, it is military focussed starting with:

“The acoustic signature is very important for small, tactical, and [medium-altitude long-endurance] military [unmanned aerial systems] that perform surveillance missions.”

So drone noise is a concern in the textbooks. Aircraft noise also has sections in my books on manned aircraft design. The noise around airports is a big problem and there is quite a bit of research going into it. Also, there is research into making helicopter blades quieter. So it will only be a matter of time before this knowledge start getting incorporated into the drones everyone can buy.

The PD-100 Black Hornet is a small, quiet personal reconnaissance drone. Photo: Richard Watt/MOD

But if we take a look at something like the PD-100 Black Hornet. The PD-100 is a small, quiet reconnaissance drone. I have been in the same room as one and it is very quiet. So it is possible to have a tiny and quiet drone. Do we want all drones to be this quiet?

Commercially available drones are not this quiet, but they are getting there. Let’s take a look at DJI. If you have heard the Phantom series of drones compared to the Mavic, you know that Mavic is noticeably quieter.

If we make commercially available drone too quiet then we might risk people perceiving them as being surveillance tools. There are already concerns about the privacy issues. Perhaps a balance needs to be struck between the noise disturbance and at alerting people to their presence for privacy issues. This is similar as to how electric cars now have to make noise when at low speeds for safety reasons.

The Future

I don’t think drone noise will be a problem in the future. With new EU regulations proposing noise caps on drones. Coupled drone manufacture’s constant bringing new models, with improved specs. These will both reduce the amount of drone noise produce.

However, there will be more drones in the hands of more people. This does mean that they will be in more places, including the quiet countryside. But, as we expect they in more and more places, then this problem will lessen.

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