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How long does a sound travel for???

olde

TRIBE Member
Technically only when it reaches a vacuum i think. The waves amplitude decreases at a certain rate, I can't remember what it is. But sound I think carries on until it's either squashed by other sound or no longer has anywhere to go (vacuum). I could be wrong physics was a long time ago.

jordan
 

Isosceles_CAT

TRIBE Promoter
It depends on a number of factors such as the original amplitude and frequency content of the sound, as well as environmental factors such as air quality. For instance, the speed of sound at sea level is generally thought to be about 344mps, but a heavy moisture content in the air will slow the sound down significantly.

When trying to measure things like this, RT60 is an important term to keep in mind. RT60 refers to the time it takes for the reverberations of a sound to decay by 60db from its peak amplitude (1/1000 of the original power). Typical RT60 times for a concert hall are 1.5 - 3 seconds.

HTH :)
 
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Humanjava

TRIBE Member
Sound travels at 344m/s or 770 Mph at 0% humidity and at sea level. The formula to determine this is:
V = 331.4 + 0.6Tc
V = velocity (m/s), Tc = temperature in Celsius.
Sound also travels through liquids and solids at different rates

 

physix

TRIBE Member
^^^ this reminds me of why i love school...

i was walking to class in the Technology Building of my
school and i heard these 3 guys arguing... and I mean
they were GETTING it!

i turn the corner and it's three guys arguing over
equations.... i have no idea what the equation was
over but i know it was enough for these nerds to
get hot over....

nerds = future money
and future money arguing over equations is HOT!!!
 

casual

TRIBE Promoter
The physical measurement of the length of one cycle is equal to the velocity of sound divided by the frequency of sound.

sound travels @ 1,130 feet per/second @ sea level [70 deg fahrenheit]

a lower sound will have a longer wavelength, and vise versa

20hz..................56.5 feet
63hz..................17.9 feet
250hz................4.5 feet
440hz................2.5 feet
1khz..................1.1 feet
6khz..................2.2 inches
16khz................0.07 inches
 

casual

TRIBE Promoter
Originally posted by Isosceles_CAT
It depends on a number of factors such as the original amplitude and frequency content of the sound,

When trying to measure things like this, RT60 is an important term to keep in mind.
HTH :)
amplitude?? don't know how this applies?

RT60-determines the reverb time of a room, doesn't apply to the length of one cycle
 
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docta seuss

TRIBE Member
oh who cares.

i'm sure the answers given thus far will suffice.

..unless anyone else is really, really yearning to share additional information from their textbooks..
 

AshG

Member
The question is worded poorly, in all fairness.

"how long" may refer to either space or time.

But in either case, since sound is only particle vibration, then the "length" of sound depends entirely on how efficient the medium is in translating the vibration.

There are far too many factors to have a definitive answer, it might also be pointed out that the speed of sound has nothing to do with this, as only the elasticity of the medium is important in determining length.

As an example, while moisture content influences a sound wave's speed, the more important question is how this might influence sound wave propogation efficiency.
Turns out, the more dense the material, the more efficient the propogation(in terms of length, not speed).
High moisture mediums actually allow sound to travel further, as you might easily see if you were to consider an extreme example, such as a body of water.
 
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Isosceles_CAT

TRIBE Promoter
Originally posted by The Electrician
How long does a sound travel for, before it's dispersed into nothingness?
OK, first lets try to make this into something we could potentially calculate. So we assume that the sound will be travelling through air of temperature X, humidity Y, and at an altitude or pressure of Z. I'm sure that there are many other factors involved but its clear these are the main ones ...anyway they have the potential to act on the way the wave moves through the air.

So next we set up the experiment. Lets assume we are in a completely open space...If we take a frequency F of amplitude A and project it in a particular direction, it will travel for a certain distance before it has diminished to 1/1000th of its original power [RT60]. Now, factoring in our 'air quality index' of x,y,z etc, and also taking into account descrete temperature changes in the air, wind speed/direction, the surface of the ground, cloudiness and about a million other variables, you could calculate an answer to the question: How long does a sound [F&A] travel for [in environment W,X,Y,Z], before it's dispersed into nothingness [RT60]?

The question has nothing to do with the length of one cycle of a particular frequency.
 
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Deus

TRIBE Member
I think a good analogy to understand this problem is waves in water. When you drop a stone into the middle of an undisturbed lake. You can observe that as the waves travel farther the less they decrease in amplitude. I think the initial question heare was meaning to ask, when does the (sound)wave's amplitude equal zero. Theoreticaly the amplitude decreases with distance and gets infinitely small but never 0. However, practicaly, we know that waves are forms of energy, and energy never dissapears, it just gets converted into other forms of energy.
 

casual

TRIBE Promoter
the question has everything to do with the life span of one cycle and absolutely nothing to do with amplitude [if it does please explain] and rt60 is in reference to the environment, how many walls or objects are defeating the sound wave? I am taking a position that you are in the dessert, with nothing around, therefore nothing to reverberate off of and therefore rt60 is irrelevant. If you want to calculate rt60 into the equation, there is no answer because rt60 is a variable sausage dependent on room size and contents. but 20hz unabstructed @70 degress F will travel 56.5 feet p/cycle.

rt60 is the measurement of reflections and dampening, nothing to do with the physical length of a sound wave

I understand that sound may linger depending on the room, but I took the question as how long it physically is, therefore its veleocity divided by frequency
 
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Isosceles_CAT

TRIBE Promoter
Originally posted by codex
the question has everything to do with the life span of one cycle and absolutely nothing to do with amplitude [if it does please explain]
Its quite simple, really. The question was not about the length of a cycle of a sound wave. Mike Richards simply threw in a fact about the length of a cycle of a 20hz wave for kicks. The question was: "How long does a sound travel for, before it's dispersed into nothingness?". Again, the question was: "How long does a sound travel for, before it's dispersed into nothingness?". As you can read, no reference to cycle or period is made.

What does 'dispersed into nothiness' mean? One would assume from context that it refers to a point when the AMPLITUDE of the sound (or wave, or soundwave) has diminished by a particular amount, known only to the mysterious author of this thread.
and rt60 is in reference to the environment, how many walls or objects are defeating the sound wave? I am taking a position that you are in the dessert, with nothing around, therefore nothing to reverberate off of and therefore rt60 is irrelevant. If you want to calculate rt60 into the equation, there is no answer because rt60 is a variable sausage dependent on room size and contents. but 20hz unabstructed @70 degress F will travel 56.5 feet p/cycle.
RT60 refers to the time it takes an impulse to decay by 60db from its peak amplitude or 1/1000 of its original power. While this is a term generally used to measure reverberation times, it also provides a more solid reference to an 'end point' of the sound in question than 'disperses into nothiness'. The point at which a sound of a particular initial amplitude can be thought to have 'dispersed into nothingness' is highly subjective, where as the point at which a sound of a particular initial amplitude reaches 1/1000 of its original power is not.
 
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