According to the Helicopter Association International (HAI), the sound level of a helicopter flying at 500 feet is approximately 87dB. At 1,000 feet, the sound level drops to 79dB.
The difference in sound level may not seem that great, but it is in fact significant, reducing the resultant noise by half its impact. This is because sound levels are measured according to a logarithmic scale.
Helicopter Noise Levels vs. Common Sounds
To get an idea of how loud a helicopter actually is, let’s consider the sound level of some common noises you might hear every day.
The lowest sound level you can hear is breathing at around 10 dB. A whisper or rustling of leaves registers at 20 dB; a conversation at home is approximately 50 dB; a passenger car traveling on the freeway at 50 ft away is 70dB. While these are all quieter than the noise a helicopter makes, the noise the food blender in your home produces is at a very similar level to a helicopter flying overhead at 88 dB.
Interestingly, people rate the sound level of a helicopter higher than it actually is – as much as 10 decibels higher in fact. This is largely due to the unfamiliar and unique sound a helicopter makes thanks to its blade vortex interaction. This noise level is similar to a farm tractor, motorcycle, or power lawnmower.
Comparison of Helicopter Noise Levels
Thanks to the U.S. Department of Transportation who released a document titled “Noise Levels and Flight Profiles of Eight Helicopters”, we can see how the noise levels of some of the most common helicopters compare against each other at takeoff, approach, and level flyover.
All readings are a measure of Effective perceived noise in decibels (EPNdB), which is used for aircraft noise certification.
- Aérospatiale SA 330 Puma: Takeoff: 95.4 EPNdB; Approach: 95.6 EPNdB; Level Flyover: 91.4 EPNdB
- MBB Bo 105: Takeoff: 89.1 EPNdB; Approach: 91.7 EPNdB; Level Flyover: 88.4 EPNdB
- Bell 206L: Takeoff: 85.9 EPNdB; Approach: 90.3 EPNdB; Level Flyover: 85.8 EPNdB
- Sikorsky S-61: Takeoff: 95.9 EPNdB; Approach: 94.0 EPNdB; Level Flyover: 92.6 EPNdB
- Sikorsky S-65: Takeoff: 95.7 EPNdB; Approach: 99.9 EPNdB; Level Flyover: 97.1 EPNdB
- Bell 212: Takeoff: 91.7 EPNdB; Approach: 95.7 EPNdB; Level Flyover: 94.6 EPNdB
- Aérospatiale Gazelle (SA 341G): Takeoff: 92.5 EPNdB; Approach: 89.5 EPNdB; Level Flyover: 86.1 EPNdB
There appears to be a correlation between the weight of the helicopter and its noise level. The Sikorsky S-65, which is the heaviest helicopter on the list at 37,000 pounds is the loudest at takeoff, approach, and level flyover. The Bell 206-L at 4,000 lbs is one of the lightest models and makes the least amount of noise at takeoff and level flyover.
How Loud Is It Inside a Helicopter?
The cabin noise of commercial aircraft today is generally lower than 80dB. However, most helicopters far exceed this limit, reaching levels as high as or even beyond 100 dB. This is particularly true of older production models and when higher power settings are used. Of course, every person inside the helicopter, whether that be the pilot or passengers is expected to wear an aviation headset to protect their hearing.
Sometimes measures are taken to reduce the noise heard inside a helicopter. If we take Marine One, which the president of the USA travels in, soundproofing is used in an attempt to dull the sound as much as possible. While the noise heard inside the helicopter is by no means silent, it is quiet enough for an elevated voice conversation.
Soundproofing older helicopters is relatively rare. There needs to be a good enough reason to do so, as well as the resources to carry out the work.