The problem of helicopters noise in cities

If you live in a dense city you might have noticed that the most overwhelming noises do not just come from the streets any more. There is a source of noise pollution that’s growing exponentially in our cities skies, the helicopters.

The problem is not new. Even as early as 1985 NASA was producing reports on the impact of helicopters in American cities. However, the exponential growth of air traffic in our cities is threatening to tip the balance in the wrong direction, with complaints to 311 about helicopter noise more than doubling year over year in major cities such as New York.

Why are helicopters so noisy?

First lets try to understand why helicopters are so noisy. One might instinctively think that helicopters run big engines and therefore that must be what generates all that noise. While it is true that the engine and transmission of a helicopter will create some noise, that’s not all. The main source of the noise helicopters produce comes from their blades, and more specifically from the aerodynamics of these blades.

Helicopter blades are designed to produce a lot of lift with relatively little engine power. To do this, they need to be large and they need to spin quickly. The blades also need to be angled so that they produce lift even when they’re not moving forward very fast. The byproduct of all these factors is that helicopter blades are also very effective at generating noise. On top of that, the blades produce high-frequency sound waves that are difficult for humans to block out.

Helicopter manufacturers have tried to reduce blade noise by altering the shape of the blades and changing the pitch of the rotor, but these efforts have only had limited success. In conclusion, helicopter blades produce noise because of their aerodynamic design, and there is no easy way to reduce this noise.

How loud is a helicopter?

When standing next to it, a helicopter can produce up to 120 dB, with the average models being closer to the 100 dB mark. Remember that decibels are a logarithmic scale, which means that each increase of 10 dB represents a 2-fold increase in loudness. Therefore, the 120 dB produced by a helicopter will be perceived as twice as loud as another source of noise producing 110dB. A a reference, 90dB is the sound level produced by a lawn mower.

Of course there are also other factors that affect the perceived noise from a helicopter, such as its speed, the distance between the helicopter and us, or the direction of the wind.

By the time it gets to 500 feet (152 meters), it’s only about half as loud as it was at takeoff (around 90 dB). And at 1,000 feet (305 meters), it’s about a quarter as loud (around 80dB). That is still louder than the average vacuum cleaner when flying at 1,000 feet… 

What type of helicopters fly over our cities?

There are several types of helicopters that fly over our cities for different reasons. Even though it could seem that all helicopters are the same, the truth is their flight patters and routes also have an impact on the noise pollution they product. For example, due to some pretty complex aerodynamical reasons, helicopters are nosier if they turn or change speeds than if they follow a straight line at a set speed.

These are the most common ones and how they affect our daily lives.

Police helicopters

Police helicopters are a common sight in many cities. In most cases, police helicopters are used for surveillance and to provide support for police officers on the ground. They can be used to monitor large crowds, search for missing persons, and track fleeing suspects.

This FAQ document from the Air Support Police Unit of San Diego covers a lot of interesting aspects about these type of units.

Police helicopters are allowed to fly at very low altitudes if needed, but will typically fly at an altitude of 1,500 during the day and 2,000 feet at night.

One may think that police helicopters are parked and only take off when needed, but in reality an average unit is airborne for around 10 hours a day. This allows them to respond much quicker to a scene when called. Starting up a helicopter isn’t fast, it usually takes 15 to 20 minutes, so being in the air when the call comes in actually saves a lot of time.

Oh, and by the way, did you know that police helicopters are exempt from noise complains per all state and federal regulations? So don’t bother calling 311 (to be fair, if a police helicopter is flying near your home, that probably means something is going on and you will want them to be there anyway).

News helicopters

Unlike police helicopters, News helicopters normally take off only when they need to. News channels helicopters usually follow something worth reporting, such as a car chase, a fire, or a protest. Although they can also used to take reporters quickly to a scene, which will then be reported on from the ground.

News channels helicopters usually will want to fly as low as possible to get the best images of whatever it is that they are reporting on. In most cases they will set orbit at around 500 feet, which is as close as an aircraft can get to a highway or low neighborhood without having to worry about power lines and other obstacles.

You may have also observed that news helicopters (police helicopters sometimes as well), don’t usually stay stationary for too long. Instead they usually move in circles around the point of interest. This is because helicopters consume less fuel when moving, and therefore can remain in the air for longer periods of time by circling the point where the newsworthy event is happening.

Tourism helicopters

Tourism helicopters provide an aerial perspective of a city that can be difficult to appreciate from the ground. They typically fly at low altitudes in order to allow passengers to get a panoramic view of the skyline and iconic landmarks around.

Tourism helicopters are arguably one of the most problematic when it comes to noise pollution or a variety of reasons:

• They land and take-off very often (with some trips being as short as 15 minutes). Helicopters not only are nosier when landing and taking off, they are also closer to the ground, which means closer to the streets, and therefore a lot louder than when they climb to higher altitudes.
• They follow the same predeterminate routes over and over again. A new helicopter following a carnival might be a disturbance for you a few times per year, but if you live near one of the tourist routes, you are going to be hearing helicopters go by tens, if not hundreds of times each day.
• Last, the demand for this type of activity is only growing over time, as prices drop and people are less afraid of this type of transportation methods.

Private helicopters

In recent years, there has been a surge in private helicopter traffic over American cities. While private helicopters offer a fast and convenient way to travel for the rich and famous, they are also a huge source of noise pollution which, unlike the police or news helicopters, the general public is having a hard time accepting. Cities like New York or Los Angeles are particularly suffering from this type of air traffic.

As our cities become more and more congested, some rich and famous have found in the helicopter a way around the long commutes and sitting in traffic. It is more and more common for these people to take a helicopter to the airport (where they will most likely fly private), or to their second residences outside of the city. If you’ve seen the HBO show Succession you know what we are talking about

To be fair, these people are doing nothing legally wrong. They have the money and they choose to spend it to skip traffic. However, the bast majority of us cant afford a helicopter ride, and therefore the bulk of people are seeing this as the rich being selfish and not caring if their own personal comfort has a negative impact on everybody else.

Conclusion

As we continue to see helicopters become more a part of our city lives, it’s important that we take a step back and consider the impact they have on our cities. Noise pollution is a real issue, and one that will only get worse if we don’t start regulating helicopter use.

Finding the right balance between safety, efficiency, and quality of life for all citizens is always tricky, but it’s a challenge we need to face head-on today, so that it doesn’t become an even larger problem tomorrow.