[meteorite-list] How far away can a meteor be heard?

From: Fries, Marc D <marc.d.fries_at_meteoritecentral.com>
Date: Thu, 9 Jul 2009 08:15:43 -0700
Message-ID: <C67B57AF.98CC%Marc.D.Fries_at_jpl.nasa.gov>

That?s a good question. There's one major difference between a
meteor-produced sonic boom and thunder - altitude. Most thunderstorms occur
below 10 km altitude while fireballs occur well up in the 20-30 km range.
That means that the fireball should propagate to a wider area, but it seems
in practice that their sonic booms are highly directional. I think its a
bit of an apples-to-oranges comparison, since thunder radiates
omnidirectionally from low altitude while fireballs "push" a compression
wave ahead of their direction of travel at a much higher altitude. Thunder
also propagates without seeing much in the way of change in air pressure,
while fireball sonic booms radiate downward through a pretty substantial
increase in air pressure.

So my answer is... It depends. (Which is almost always the answer to a
scientific question!) People directly along the path of a fireball should
hear something louder than those off to the sides, I would expect. In
principle a fireball's sonic boom should also travel farther since it starts
higher up, but I suspect that propagating downward and outward through
increasingly thicker atmosphere would serve to deflect and diminish it.

I bet that research into airburst nuclear weapons blasts included modeling
of shock waves and would be very useful for answering that question, but I'm
thinking that we're not going to get a look at that data any time soon.
Just a hunch.



On 7/9/09 7:39 AM, "drtanuki" <drtanuki at yahoo.com> wrote:

>
>
> List,
> I have the answer for thunder but not a meteor (I am guessing that they are
> about the same? 10miles or 16km
>
> Chris or anyone care to give the correct answer? Thanks!
>
> Thunder contains a somewhat cylindrical initial pressure shock wave along the
> lightning channel in excess of 10 times the normal atmospheric pressure. This
> shock wave decays rapidly into a sound wave within feet or meters. When
> thunder is heard from about 328 feet (100 m) distance, it consists of one
> large bang, yet hissing and clicking may be heard just prior to the bang
> (upward streamers). When heard at .6 mile (1 km) from lightning, thunder will
> rumble with several loud claps.
>
> Thunder is seldom heard beyond 10 miles (16 km) under ideal conditions. The
> sound of distant thunder has a characteristic low-pitched rumbling sound.
> Pitch, the degree of highness or lowness of a sound, is due to strong
> absorption and scattering of high-frequency components of the original sound
> waves, while the rumbling results from the fact that sound waves are emitted
> from different locations along the lightning channel, which lie at varying
> distances from a person. The longer the lightning channels, the longer the
> sound of thunder. Humans hear frequencies of thunder between 20-120 Hertz
> (Hz). However, there is a small amount, less than 10%, that is inaudible to
> humans produced from lightning, called infrasonic. Special listening devices
> are required to record these inaudible sounds.
> Sources: http://www.lightningsafety.com/nlsi_info/thunder2.html
>
> Best Regards, Dirk Ross...Tokyo
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Received on Thu 09 Jul 2009 11:15:43 AM PDT