Why does the thunder from close lightning produce a BOOM and then a slow fade off? Why does it fade off instead of just stop? Conversely, why is thunder from far away a slow fade-on instead of an instant but quieter boom?

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Why does the thunder from close lightning produce a BOOM and then a slow fade off? Why does it fade off instead of just stop? Conversely, why is thunder from far away a slow fade-on instead of an instant but quieter boom?

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Anonymous 0 Comments

Thunderstorms are one of the most special experiences I’ve had. Like a unique blend of fear, awe, humility, respect, and curiosity, and excitement. It’s truly a natural shut the fuck up and pay attention experience for me.

Anonymous 0 Comments

It’s like ripples in a pond the sound waves get bigger the further it gets away from its initial point

Anonymous 0 Comments

Throw a brick into a pond. One very sudden impact, and over before you know it, but the waves ripple out and about for minutes. Something doesn’t have to be happening all the time for its consequences to be happening all the time.

As for the fading, notice how the waves are taller close to where the brick hit, and flatten out as they move further away from the brick and stretch out.

The same happens with lightning. It stirs up the atmosphere in a moment, but the waves in the atmosphere behave almost exactly like the waves in water: be nearby and you hear a tall wave (a lot of compressed air), be further away and you hear a short wave (less compressed air, because it spread out and evened out more before reaching you).

Anonymous 0 Comments

Not an answer so hopefully this doesn’t get removed but I live in Alpine NZ and when we get thunder it echoes through the hills, sometimes you can hear it for a very very long time.

Anonymous 0 Comments

Same reason a car that’s driving away gets quieter, it’s travelling away from you.

If it stopped instantly, it would be travelling so fast that you’d be dead from the air being so hot, due to friction.

Anonymous 0 Comments

The same reason why the ripples in a pond fade away when you throw a rock in it. The traveling wave dissipates over time as it expends energy moving outwards.

Anonymous 0 Comments

Correct me if I’m wrong ng but it’s like a car. Close your eyes when a car is passing by you. While it’s close it’s louder and it fades away as it gets further

Anonymous 0 Comments

With close thunder, you mostly get a loud sound with reverb (or minor, overlapping echoes that sort of extend out the original sound). This fades away over time.

Distant thunder, however, gets some really complicated stuff with how over very large distances and with very loud sounds different sounds will have a different reverb spread that will fade in and out and almost all of the sound energy will be reverb. Suffice to say, you’ll get most of the early part of what you hear being a bit higher pitch which doesn’t stay as loud after traveling before the low end that will keep its energy over vast distances hits.

Anonymous 0 Comments

Because it’s a wave of energy moving past you. A close wave has no ability to roll on; you’re too close to it’s propagation.

Edit: National Weather Service has the best answer. It’s from the heat of the lightning causing rapid expansion of molecules at each little point of the lightning as it shoots to the ground and branches off from the main ‘trunk’ of lightning –

>Regardless of whether lightning is positive or negative, thunder is produced the same way. Thunder is the acoustic shock wave resulting from the extreme heat generated by a lightning flash.

>Lightning can be as hot as 54,000°F (30,000°C), a temperature that is five times hotter than the surface of the sun! When lightning occurs, it heats the air surrounding its channel to that same incredible temperature in a fraction of a second.

>Like all gases, when air molecules are heated, they expand. The faster they are heated, the faster their rate of expansion. But when air is heated to 54,000°F (30,000°C) in a fraction of a second, a phenomenon known as “explosive expansion” occurs. This is where air expands so rapidly that it compresses the air in front of it, forming a shock wave similar to a sonic boom. Exploding fireworks produce a similar result.

So a firework, as they describe, only has one point of propagation of the sound wave. [Lightning, however, propagates sonic booms / shock waves over and over and over as it races to the ground and branches off](https://www.weather.gov/images/jetstream/lightning/thunder1.png).

They also added –

>In addition, the temperature of the atmosphere affects the thunder sound you hear as well as how far away you can hear it.

>Sound waves move faster in warm air than they do in cool air. Typically, the air temperature decreases with height. When this occurs, thunder will normally have an audible range up to 10 miles (16 km).

>However, when the air temperature increases with height, called an inversion, sound waves are refracted (bent back toward the earth) as they move due to their faster motion in the warmer air. Normally, only the direct sound of thunder is heard. But refraction can add some additional sound, effectively amplifying the thunder and making it sound louder.

>**How warm and cool air affect the sound of thunder**

>This is more common in the winter as thunderstorms develop in the warm air above a cooler surface air mass.

>If the lightning in these “elevated thunderstorms” remains above the inversion, then most of the thunder sound also remains above the inversion. However, many of the sound waves from cloud-to-ground strikes remain below the inversion giving thunder a much louder impact.

Anonymous 0 Comments

High frequency sound (the crack) is filtered more by the atmosphere across distance than the lower frequency (rumble).

See Zahorik, Brungart, & Bronkhorst, 2005 for an in-depth review of Auditory Distance Perception research