When dry leaves blow around on a windy day, it creates rustling noise. By physics, sound is created when the disturbance waves travels at the speed of sound in the medium. Also, the speed of the wave is dependant on the pressure change in the medium. Collaborating all these, the question is, does the leaves contact with the ground have so much pressure change in the surrounding?

Question

owlfred · Answer

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anonymous · Answer

A friend of mine told me that the threshold of hearing is 20 micro-pascal (rms, 20 * 10^-6 Pa). Compare that with atmospheric pressure - 100kPa (10^5 Pa). The slightest sound we can hear has a pressure nearly only 1/5000,000,000 times the atmospheric pressure. The leaves don't have to create all that much pressure change for us to hear.

anonymous · Answer

Threshold? isnt threshold of hearing in Hertz? 20hz-20khz? how is it dependent to pressure? and the explanation from there holds reasonable.

anonymous · Answer

That is the frequency threshold. There is also an additional loudness threshold

anonymous · Answer

ok. if you can provide me some credible source to refer to your claim, it would do me great help. Otherwise, thanks a lot for the reply.

anonymous · Answer

I actually heard this from my friend - who happens to be a rocket engineer. I also saw the same figure on wiki: http://en.wikipedia.org/wiki/Sound_pressure I know that the above two don't really count as credible. But then, this site[ http://www.sengpielaudio.com/TableOfSoundPressureLevels.htm ] also refer to the same figure. Hope that helps

anonymous · Answer

As a matter of fact, this site has enormous amount of info into audio and audio processing. I am just leaving the link here so that someone may find it useful: http://www.sengpielaudio.com/Calculations03.htm The key part is under the title 'Sound Pressure Levels'.