Assume? I rarely assume, but I did look it up. According to
https://en.wikipedia.org/wiki/Speed_of_sound The speed of sound is the
distance travelled during a unit of time by a sound wave propagating
through an elastic medium. In dry air at 20 °C the speed of sound is
343.2 metres per second.
Where do you get 333 m/s?
David Pearl MetricPioneer.com 503-428-4917
----- Message from [email protected] ---------
Date: Wed, 26 Jun 2013 20:17:21 +0100
From: Martin Vlietstra <[email protected]>
Reply-To: [email protected]
Subject: [USMA:52992] RE: Flash To Bang (Lightning Distance)
To: "U.S. Metric Association" <[email protected]>
Assume that sound travels at 333 m/s. The sound will travel one kilometre
in three seconds.
From: [email protected] [mailto:[email protected]] On Behalf
Of John M. Steele
Sent: 26 June 2013 12:45
To: U.S. Metric Association
Subject: [USMA:52990] Flash To Bang (Lightning Distance)
Interesting article on estimating the distance to a thunderstorm:
http://www.livescience.com/37734-how-far-away-is-lightning-distance.html
She starts with the usual 5 seconds per mile, but she does include a metric
version. I'm not sure I want to multiply by 340 m/s in my head, however.
It might be easier to just divide by 3 for an approximate (and slightly
conservative) distance in kilometers.
She mentions, but perhaps doesn't adequately explain, the variation of the
speed of sound with temperature. That may be why she gives two values, only
one sentence apart. The lower figure is correct at 0 °C, the higher figure
near 20 °C (remember it is cooler aloft, so the sound is arriving via
multiple paths with differing, generally unknown, temperature profiles).
----- End message from [email protected] -----
