I have looked at this and this, both discussing the subject as a matter of atmospheric pascals. (Is that redundant?)
The first cite was ragged on by a number of people and the second gave “194 dB” as the largest sound by “natural means,” implying a limit given by air, period.
Quora is OK, but I’d walk a mile for a GQ. Could someone splain the case?
Thanks.
The amplitude of the sound wave is how much the pressure is changed from the ambient pressure upward and downward to the max and min pressures in the sound wave. Since the min pressure cannot be less than zero, the greatest possible amplitude equals the ambient pressure. “Decibels” are a logarithmic measure (10dB is a change in amplitude by a factor of 10) so the mathematics your first source shows is this calculation: ten times the log-base-10 of the ratio of the number of pascals in “one atmosphere” (the typical ambient pressure at sea level) over the number of pascals defined as the “zero decibels” level (“threshold of hearing”, the amplitude which a healthy human can typically just-barely-hear; vibrations lesser than that are actually negative-decibel sounds).
If the atmosphere had higher pressure (say, deep within Jupiter), more powerful sounds could be carried.
Thanks. But I’m still confused: some physical impetus is given to the atmosphere such that compressive waves are generated. There is a limit to what the physical power can be?
That can’t be right. I think I’m having trouble (again) on “sounds.”
Is a louder sound thus possible underwater (at a depth where pressure exceeds one atmosphere)?
There’s a limit how much the atmosphere can propagate in a particular form, namely alternating low and high pressure bands. Once the atmosphere has been blown away from the low pressure band to the point that it is vacuum, then you can’t apply further impetus to air, when the air isn’t there.
That only describes how low the pressure can go, it says nothing about the limit of compression or how high a pressure a sound wave and sustain.
So does this mean that the loudest sound in ‘mile-high’ Denver will sound to humans quieter than the same sound at sea level?
The vacuum limit would be relevant to how loud a sustained sinusoidal sound could be, but many sounds have short and unsymmetrical waveforms. Explosions are, or are associated with, brief sounds whose pressure excursions are many atmospheres in amplitude (mostly upward of course).
Ok. Here’s [“sound” as sustained sinusoidal wave] v. [“sound” as pressure excursions].
I understand the former “sound” as a self definition. What is the latter–a shock wave?
I think I’ve been corrected in another thread, about “phonons,” and that all matter “transmits” them–and then the thread had some weird comment from Chronos on phonons travelling on electrons.
But it obviously didn’t take. 
“Shock” wave or “blast” wave are common terms for these irregular events in which the overpressure can go way way above 2 atmospheres; in a sustained symmetrical propagating wave, the overpressure can’t go above 2 times the ambient pressure because the underpressure can’t go below 0.
I was going to say a fart in church, but that’s not what you’re getting at.
Perhaps the Russian meteor and it breaking the sound barrier is a case in point.
(Bolding mine)
Actually, for sound pressure levels, 20 dB represents a factor of ten, 10dB is for sound energy.
I think typical usage for decibels is horribly messy. A bel is a factor of ten, and a decibel is one tenth of that, or 10^0.1. In anything. Anything at all. Just like doubling anything makes it twice as big.
Some things are related to others as squares or square roots. If you double the voltage through a resistor, the current also doubles and the power therefore quadruples.
What is so messy is that people will measure voltage or pressure ratios and then discuss wattage or sound energy ratios that vary as the square of the thing they are measuring (assuming the relation holds in the case they are treating). Well, if you increase voltages by a factor of ten, then for a resistor the power will increase by a factor of a hundred, and a tenfold increase is ten dB and a hundredfold increase is twenty dB.
But the twenty isn’t built into dB as a unit, and there is nothing special about the number twenty from the point of view of thinking about decibels.
Therefore I propose never putting “20” and “dB” near each other in a sentence, and thrashing those who do.
Sorry, I got a bit carried away. I’m a good friend of the Neper, you see, and these things kind of get to me.
I am not sure but I read somewhere recently that a sperm whale’s “click” is well above 200db. Which is REALLY loud!
“…an Earth-shattering Kaboom!”
dB what? By itself, dB is just a ratio, only when paired with a reference does it become a unit like dB SPL (reference 2*10^-5 Pa) or dBu (reference 0,775 V). There is no air pressure under water, so what would those 200 dB relate to? I’m not questioning that it’s a really, really loud noise, but that number doesn’t really mean anything.
Has no answer because some are talking tomatoes & some are thinking celery.
What is sound? A pressure wave of air that we hear? A pressure wave of water that ‘ears’ can translate to ‘sound’ in our brains?
Does some sound dissipate because moving molecules takes energy?
Stand next to the so far strongest, and sharpest whatever pressure wave man can make and it blows out your ear & all ears on the planet of all things that can detect pressure waves. Is there a sound? ( Tree & Forrest Q also)
So, is their a limit on the size or power of a pressure wave? Or on the ability to detect that pressure wave?
Now sticking to what humans can ‘hear’ & how to measure? Make as pressure wave and measure it at all distances that human can detect it with ears. Say that is from one foot ( closer blows the ear so bad & fast the brain can not recognize it as sound ) out to 101 feet where the most sensitive ear can not hear it. Anything off either end of the scale is sound also?
We can use machine to detect these pressure waves in air & water & jello & cranberry juice outside of what our ears can do and these pressure waves are also sound? Well, human ears can ‘hear’ in those mediums so it should be called as sound, right?
Speed through the medium can be measured so but can maximum pressure be stated absolutely?
Just because a medium can be made to go to zero ( nothing there ) it does not follow that it can not be compressed all the way to the next state. ( liquid air or it’s components ) but as with liquid mediums, not so much.
So we need to now define volume. For who or what? Sound? We have already blown out all ears on the planet and so… hummm Have we circle all the way back yet?
Can a sound be made that is more than twice 20 DCB’s move more than one wave length in the standard air medium?
IMO, the loudest volume of sound is one which does not destroy hearing. ( level of ? )
The biggest pressure wave in air it is possible to make has not been done yet.
Side note:
If a pressure wave or sound ( your pick ) is slow enough that I can equalize my ears so as to not destroy my ability to hear, is that a loud sound or a slow sound?
Rats, now there is the added problem of speed of the wave due to it’s medium. )
Enough !!! I’m off to think about cheese… :smack:
A phonon is just a quantum of sound, in an analogous way to how a photon is a quantum of light. That is to say, under some circumstances, sound can behave as made up of particles, and we call those particles phonons. So anything that can transmit sound can transmit phonons. That would surely include electrons, and I’m pretty sure that there are some applications in solid state physics where that’s particularly significant, but that’s not really my field.