Airplanes, which were seen as just a dream until recently, have become one of the biggest tools in the functioning of our lives today. While the speed and comfort of aircraft are constantly improving with new technologies, aircraft engineering has become one of the peak points of engineering.
Well, how do the planes, of which we see dozens of them in the sky every day, manage to make their voices heard when they fly thousands of meters above the ground? More importantly, how come we don’t hear this sound when we’re inside the plane? Let’s give answers to these questions.
First, let’s learn about the sources of noise in airplanes:
Of course, we need to look at the source of these sounds in order to learn how we hear the sound in airplanes. Noise from airplanes in flight is usually caused by the following factors:
- Aircraft running engine
- Propellers that are responsible for taking air into the engines and rotate thousands of times per second.
- Airflow with high thrust from the back of the engine,
- Aerodynamic sounds produced by the movement of the aircraft in the air (same logic as the wind noise you hear when driving)
- Vibration in the fuselage caused by the engine and airflow
So, how can we hear the sound of planes flying hundreds of meters above us when we are on the ground?
You know how loud the planes make, especially at airports. In fact, if you are entering the plane not with a bridge but with a ladder from the ground, you can hear this sound uncomfortably. But in fact, this sound is only a small part of the sound the plane makes while flying. Because the noise you hear when the planes are on the ground is only caused by the engines running at the lowest level.
Of course, this situation changes when planes are in the air. The engines run at maximum power, especially during takeoff and when it rises to flight altitude. In addition, the plane pierces the air, almost creating a wind. Therefore, the sound we hear from the ground as airplanes fly is mostly made up of the sound of the air and the engine.
Of course, how loud the sound sounds to us depends on many factors. In particular, air temperature, humidity and pressure play a major role in the propagation of sound waves. Likewise, the altitude of the aircraft is of great importance as the pressure changes according to the altitude.
The fact that we do not hear the sound of the planes, behind which we see ‘white smoke (condensation trace)’ in the sky, is due to this height factor. The sound of planes flying at 9,000 meters and above loses its intensity as it approaches the earth. If there is no sound around you, you can actually hear this sound at a low rate. But if you are in the city, this sound cannot be heard because of other sounds.
Aircraft manufacturers continue to make continuous improvements to reduce the sound that can be heard from outside the aircraft. You can experience this even at airports when an old model passenger plane or a new model plane takes off.
So how is this sound prevented inside airplanes?
In fact, the sound of airplanes cannot be completely prevented inside the airplane. However, thanks to the methods developed over the years, most of this sound is not reflected on the passengers, the sound is reduced to a healthy level. Especially in the early days when jet engines started to be used in passenger planes, the sound inside the plane was extremely disturbing.
Aircraft manufacturers resort to innovative methods to prevent the sound from reflecting inside the aircraft. This sound, which can cause permanent damage to your hearing under normal conditions, is now destroyed by the following methods:
- Sound insulation materials placed between the inner and outer structure in the fuselage of the aircraft
- The content of materials such as seats and plastic inside the aircraft
- Body designs regulating the air flow on the fuselage of the aircraft
- Structures that prevent the propagation of sound at the ends of the engines and especially behind them
- Enlarging engine propellers and running at slower speed
Just like when we hear it from the ground, the sound we hear inside the plane is actually the sound of the air to a large extent. Manufacturers are turning to body designs that will reduce the noise in the cabin in the design of the aircraft.
Sound insulation materials used between the inner and outer layers of the aircraft fuselage are also of great importance in terms of engineering. These materials have to be as light as possible, while providing as much sound insulation as possible. Therefore, companies conduct many scientific tests for the development of this material, cooperate with third-party insulation companies.
We can actually see how much noise there can be inside an airplane on smaller airplanes. Planes like the Piper J-3, known as the bush plane, have no sound insulation, while planes like the Cessna have very little insulation. The occupants of these planes have to wear noise-canceling headphones to protect their ears.
Therefore, the next time you get on the plane, don’t forget to thank the effort spent and the new technologies developed to ensure that you have a comfortable flight experience.
- Sources: BBC, Skandia Inc, Soundproof Cow, Boeing
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