What’s all the buzz about?

It’s pretty clear that the age of drones is dawning. They are going to play an important role in the future – both in industrial and consumer worlds. In fact, within industry, drones are already successfully used. They are abundant in the entertainment industry for filming, and within the oil & gas and utilities industries for remote monitoring. With consumers, their use has mainly been recreational, but that’s all about to change.

In April, the UK government started a pilot delivery scheme with Amazon, and in March, UPS drone delivery subsidiary UPS Flight Forward announced a collaboration with German drone-maker Wingcopter to develop the next generation of package-delivery drones.

It’s surely only a matter of time, then, before they are a common sight – and sound – in our skies. And therein lies the problem: their incessant and unmistakable whine, which, according to a study by Nasa, is found to be more annoying than the sound of cars. In a world full of drones, will we be able to hear ourselves think?

Noise is a major issue. Not only is it irritating, it is also detrimental to health, having psychological effects and a wider effect on a person’s overall wellbeing. Exposure to noise has been linked to sleep problems and heart disease, and according to the European Environment Agency (EEA), at least 10,000 cases of premature deaths from noise exposure occur each year. It also has a significant impact on wildlife.

The EEA defines environmental noise as unwanted or harmful outdoor sound and is a product of transport and industrial activity on land, in the air, on waterways, and on oceans. The World Health Organization (WHO) reports an onset of adverse health effects in humans exposed to noise levels at night above 40dB.

Drones come in many shapes and sizes, including larger fixed-wing unmanned aerial vehicles with wingspans of a few metres and weighing over 150kg, smaller multirotor devices which weigh less than 1kg, and hybrid variants. The average drones have noise levels of between 70-80dB(A) in flight.

“The causes of the noise can be broken down into four main parts: the size of drone, the mechanical/aerodynamic noise, electrical noise and perceived noise,” says Alan Perrin, chief drone pilot at Helicopter Film Services. “As the size and weight of the drone increases, so invariably does the noise. However, interestingly, the larger drones, with larger and slower turning propellers, create a much lower pitch and seemingly more acceptable noise level.”

Charles Tavner, executive chairman at Flylogix, goes on to explain that it’s not only the noise level you have to consider, but also the way the noise behaves. “There’s also the nuisance factor – does the sound appear suddenly or is it predictable? Is it there persistently? One of the issues with multirotor devices is that they tend to hover in one place, so they are close to you for a longer period of time.”

“Operating a drone over a small area and at low speed can create a higher level of perceived noise, as the monotone of the rotors lingers, and with added obstacles like walls, corridors or buildings, perceived noise can be much more than what the drone itself actually produces,” says Perrin.

Noise management is big business and responsible manufacturers are making their machines as quiet as possible. “Drones flying today are all as quiet as they can reasonably be, as excessive noise being produced would point to inefficient design and energy being wasted,” Perrin explains. “As we see drones being requested to carry out more and more ‘worker’ tasks, their weight has started to increase to provide more capabilities, but this will also present a challenge in terms of noise. Perhaps the best approach is to reduce the pitch of the noise to a less intrusive and more acceptable level.”

Noise is an essential point to consider if drones are going to become socially accepted. According to Tavner: “As the industry starts to mature, and we move on from proof of concepts, the bigger, more responsible operators are getting more involved in these types of questions and the practicalities.”

Furthermore, noise isn’t the only issue to consider for drones. There are a number of other factors that need to be raised including where are the drones going to take off from and land, where are they going to refuel and what should their frequency of operation look like?

Tavner says: “There are many practical and logistical points to think about when companies are running routine services such as which airfields are configured for lots of unmanned traffic. There’s also the environmental impact on wildlife to consider. For example, we modify our flight patterns to avoid resting places of migrant birds.”

He points towards work that is being done through the UK government’s Future Flight Challenge, which has been set up to enable widespread, safe use of new aviation vehicles, at the same time as helping the wider aviation system to develop upgraded physical, computer and regulatory infrastructure. It aims to revolutionise the way people, goods and services fly and support the development, in the UK, of new technologies from freight-carrying drones to urban air vehicles to hybrid-electric regional aircraft.

There is no doubt that the drones are coming and, by the sound of it, the industry is making all the right noises in relation to minimising the buzz. That should be music – or peace – to our ears.