Naked Science Forum

Life Sciences => The Environment => Topic started by: James on 23/06/2009 11:30:02

Title: Do sounds get louder just before a storm?
Post by: James on 23/06/2009 11:30:02
James asked the Naked Scientists:
   
Hi Chris,
 
One of your listeners earlier noticed that sounds seemed to be dampened down when it's foggy (http://www.thenakedscientists.com/HTML/content/questions/question/2327/).  
 
I've noticed the opposite effect when the weather is stormy, ie just before a thunderstorm, that sounds actually appear to get louder & travel further!  Is this true, or is it just my imagination?  
 
Regards,
 
 
James in Cambridge.

What do you think?
Title: Do sounds get louder just before a storm?
Post by: paul.fr on 23/06/2009 14:33:43
I can't say I've noticed this, and I wonder if it has anything to do with "calm before a storm"?

More often than not, before thunderstorms we experience high humidity. As sound travels faster in humid air I wonder if the sound is not louder, but reaching you sooner and therefore appearing louder?

Maybe a passing physicist can answer this better.
Title: Do sounds get louder just before a storm?
Post by: WylieE on 24/06/2009 02:58:54
I used to live close (too close) to a train track and there was a big change in the sound of the train whistle depending on how humid it was.  I can't say if it was louder or not, but very distinct, less "tinny" and more fluid sounding on a humid day than a cold, dry day  (the only time it was not humid was when it was cold). 

There was also a change between winter (in Michigan, so below freezing) and summer.  I love the above freezing train sound because it means summer is coming.

Of course it was always louder in summer, I had my windows open  [:-\]

Title: Do sounds get louder just before a storm?
Post by: RD on 24/06/2009 05:01:07
Could be refraction ... http://www.school-for-champions.com/science/sound_over_water.htm
Title: Do sounds get louder just before a storm?
Post by: Make it Lady on 24/06/2009 20:26:23
Would the higher pressure have anything to do with it? I'm not a physicist either but I'm sure if one were passing they would give a doppler effect!
Title: Do sounds get louder just before a storm?
Post by: RD on 25/06/2009 01:29:37
A local change in atmospheric pressure would alter the refractive index and redirect the sound...

Quote
The sound of thunder created by lightning may be refracted upward so strongly that a shadow region is created in which the lightning can be seen but the thunder cannot be heard. This typically occurs at a horizontal distance of about 22.5 kilometres (14 miles) from a lightning bolt about 4 kilometres high.
http://www.britannica.com/EBchecked/topic/555255/sound/63980/Refraction
Title: Do sounds get louder just before a storm?
Post by: James 1 on 25/06/2009 18:20:21
The humidity idea sounds plausible, although it seems to conflict with the original question, about sounds being muffled in foggy conditions.  Having said that, I suppose fog particles being tiny droplets of water, rather than water vapour, would have a different effect on sound. 
Title: Do sounds get louder just before a storm?
Post by: Make it Lady on 25/06/2009 20:16:47
I love this question. It was really high pressure last night and I could hear the distant main road last night. No wind so it wasn't that. It has really made me listen and think. Thanks James. You I like.