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I don't think the space shuttle counts because the question was about natural sounds, not man made. 

db

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> On Mar 16, 2015, at 12:41 PM, "Richard L. Hess" <[log in to unmask]> wrote:
> 
>> On 2015-03-16 9:38 AM, Tom Fine wrote:
>> 
>> This brings up a question for the house -- what is the loudest naturally
>> occuring sound as far as SPL's -- a massive earthquake, a massive
>> hurricane or tornado, or the thunder after a big nearly
>> lightening-to-ground strike (or perhaps the thunder overhead after a big
>> cloud-to-cloud strike)? As far as human hearing goes, I'd think thunder
>> would sound loudest, but I wonder if earthquake is most SPLs because of
>> the subsonic waves?
> 
> Hi, Tom,
> 
> I hate to intrude, it is a nice thought, but we are comparing apples to bananas (despite the apple banana that is available in Maui).
> 
> SPLs are generally measured in a specified manner, but hugely different numbers will result depending on which parameters are selected. This occurs both in the time and in the frequency domain.
> 
> SPL meters can be set to slow/fast/peak (or some similar group of settings). Their frequency response can generally be set to A/B/C/Flat where the letters define specific curves. A-weighting kind-of-sort-of matches the ear's sensitivity at moderate loudness levels and has a significant low-frequency rolloff.
> 
> Calculus is involved in measuring the area under a curve which corresponds to energy which is power over time. When discussing events that last milliseconds vs. events that may last a minute or more, there are vastly different amounts of energy.
> 
> A tornado, for example, is moving and the centre of noise is moving with it, so should the SPL meter be measuring the noise in one place or should it be on the storm chaser vehicle?
> 
> From what distance should the sound be measured? As you know, direct sound falls off via the inverse square law. In enclosed spaces, that falloff stops when the reverberant field takes over. That could happen in valleys with thunderstorms.
> 
> Without knowing too much, I think that I'd vote for the Space Shuttle launch as the most energy under the curve for a relatively extended period of time as well as some very high peak amplitudes--enough to cause cavitation in the air.
> 
> A very nearby thunderclap may have a higher peak, but it's over very quickly. I do not recall any hugely loud noises from the earthquakes I've been through.
> 
> Interesting question! Thanks.
> 
> Cheers,
> 
> Richard
> 
> 
> 
> -- 
> Richard L. Hess                   email: [log in to unmask]
> Aurora, Ontario, Canada                             647 479 2800
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