Accompanied by lightning and rumbling thunder. Sounds like thunder. There are two kinds. One is thunder as clear and loud as an explosion, which is generally called "thunderbolt"; The other is muffled thunder, which some people call "muffled thunder". There is also a low and persistent rumble, which is a bit like the sound made when grinding. People usually call it "La Morey", which is actually a form of muffled thunder.
The air in the lightning passage suddenly rises sharply, making its temperature as high as 15000-20000℃, thus making the air expand rapidly, and the air pressure near the passage can be increased to above 100 atmospheric pressure. Then, it cools rapidly, the air shrinks rapidly and the pressure drops. This sudden expansion and contraction occur in a short time of a few thousandths of a second, so at the moment of lightning explosion, a shock wave will be generated. The shock wave propagates in all directions at the speed of 5000 m/s, and in the process of propagation, its energy decays rapidly, while its wavelength gradually increases. 0. 1-0.3 seconds after lightning, the shock wave evolved into sound wave, which is the thunder we heard.
There is also a saying that thunder is the sound of explosive gas produced by the decomposition of air and water vapor molecules under the action of high-voltage electric spark. Thunder and explosion sound waves are the same in the first few tenths of a second. The speed of this explosion wave is about 5000m/s, and after 0. 1-0.3 seconds, it becomes an ordinary sound wave.
People often say that thunder is generally the sound of cloud-to-ground lightning that is very close to the observer. In this case, the observer hears the thunder almost immediately after seeing the lightning; Sometimes even thunder is heard at the same time as lightning. Because lightning is near the observer, the explosion wave it produces has not evolved into ordinary sound waves, so it sounds like an explosion.
If lightning strikes in the cloud, thunder is reflected in the cloud many times, and when the explosion wave is decomposed, many sound waves with different frequencies are generated, which interfere with each other and make people sound dull. This is the muffled thunder we heard. Generally speaking, the loudness of muffled thunder is less than that of thunder, and it is not as scary as thunder.
Larmor thunder has been a dull thunder for a long time. The main reason for the long duration of thunder is the multiple reflections of sound waves in the cloud and the influence of multiple lightning strikes at different distances. In addition, when sound waves meet peaks, buildings or the ground, they also reflect. Some sound waves are reflected many times. These multiple reflections may first reach our ears, and then in a short time interval. At this time, when we speak, we feel that the thunder is dull and long, like a feeling of pulling.