By Admin 
When the night is deep, the roads are deserted and the sky is clearly visible, in such a situation an airplane passing overhead is often seen, but its sound is not heard that clearly, whereas usually even small noises are heard clearly at night. Then why is it that the aircraft which buzzes during the day gets lost in the silence of the night? Do planes really make less noise at night, or is there a scientific reason behind it?
Why is the sound of aircraft less audible at night?
It is generally believed that every sound is heard more clearly at night because the surrounding noise is less. This is true to a large extent, but in the case of airplanes there are many different reasons at work. The first reason is the number of flights. In many cities, the number of flights at night is reduced compared to the day. Governments and airlines try to prevent people from losing sleep. If there are fewer flights then naturally the noise will also be less.
Altitude and flight mode
Most of the aircraft are on long distance flights at night and they fly in cruise mode at an altitude of 30,000 to 40,000 feet. The sound coming from such a height becomes very weak by the time it reaches the ground. When the aircraft takes off or lands, its noise is high because the engines work at full power, but after reaching altitude, the engines run at a constant speed, due to which the noise is less felt.
Effect of wind direction and temperature
The temperature and wind direction in the atmosphere change during night. Sometimes a layer of cold air forms in the upper layers, which affects the propagation of sound waves. Due to this, the sound does not reach the ground directly or its effect is reduced. The propagation of sound completely depends on the weather and wind speed. That’s why sometimes the sound of airplanes is heard at night, but often it is not.
effect of being indoors
Most people are inside homes at night. Doors and windows remain closed. The fan or AC is running. All these things help in blocking outside noise. If the sound of the same plane is heard while standing in an open field or on a road during the day, it may be felt more.
modern engine technology
In today’s time, the technology of aircraft engines has advanced a lot. New generation jet engines make less noise than old engines. Such changes have also been made in the aircraft design so that sound spreads less. Even under international rules, airlines have to follow noise control standards. This is the reason why modern aircraft are considered relatively quiet.
How much noise reaches the ground at night?
When the aircraft is flying at an altitude of 30,000-40,000 feet, the noise heard on the ground is usually between 50 to 70 decibels. This level can be as much as normal traffic or a conversation between two people. Although the noise level near the airport at the time of takeoff and landing may be higher than this, the noise of the aircraft flying at high altitude remains much less.
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