The perception of airplanes sounding distant or appearing to get closer and louder as they fly over your house is a result of several factors related to the physics of sound and the aircraft's flight path.
Distance: When an airplane is far away, the sound it produces has to travel a greater distance to reach your ears. This can make the sound seem quieter or more distant. As the airplane gets closer, the sound waves have a shorter distance to travel, resulting in a perceived increase in volume.
Flight path and direction: The trajectory and flight path of the airplane also play a role. If an airplane is flying directly overhead, the sound waves reach your ears more directly, leading to a louder perception. On the other hand, if the airplane is flying at an angle away from your location, the sound waves spread out, resulting in a decrease in perceived volume.
Doppler effect: The Doppler effect is another phenomenon that influences the perceived sound of a moving object, such as an airplane. As an airplane approaches you, the sound waves are compressed, resulting in a higher frequency and a perceived increase in volume. Conversely, as the airplane moves away, the sound waves stretch, leading to a lower frequency and a perceived decrease in volume.
These combined factors can create the impression that an airplane is getting louder and closer or even give the illusion of an imminent crash. However, in reality, the aircraft is likely maintaining a safe distance and following its intended flight path.