Speed of Sound in Air as a Function of Temperature

[Paulene Gueco]

Hi, guys! :) I do hope I am posting on the right thread here.

So anyways, I'm looking into a certain topic: "Speed of Sound in Air as a Function of Temperature".

Any thoughts on how I could do this experimentally?

Warm regards,
Paulene :)

 

[Doug Huffman]

Set up a resonant air column and vary the air temperature to effect the resonant frequency.

 

[Paulene Gueco]

Wow! I didn't expect to get an immediate reply. Thank you, Sir.

Would you be so kind to elaborate a little further as to how I may be able to set up an air column? :(

 

[Doug Huffman]

A whistle.

 

[Paulene Gueco]

My Physics supervisor asked me to look into the topic for my Physics Extended Essay. I was thinking of maybe relating it with Airplanes and how they possibly break sound barriers? If that makes any sense?

 

[Doug Huffman]

Airplanes near the speed of sound are resistant to experiment.

Do you know the effect of temperature on the speed of sound in theory?

 

[Paulene Gueco]

Awwww. So supposing I disregard that mentality and follow through with your suggested experiment, what research question could I formulate, Sir?

 

[Doug Huffman]

How does resonant frequency vary as temperature of air column? First do it qualitatively as you learn your equipment, heating causes rise or decline ins resonant. Acquire instruments for temperature and audio frequency and refine.

 

[Paulene Gueco]

Oh, okay. Thank you very much, sir! I have a meeting with my Supervisor this Sunday and I have yet to find out what he thinks about it. If you've got any other suggestions, please let me know. It doesn't really have to be related to this topic, just something that's not too simple nor complex enough to do an experiment on.

Truly appreciate all your help.

Warm regards,
Paulene

 

[Paulene Gueco]

And also, I've looked into the speed of sound with regards to the temperature. The lower the temperature is, the faster the travel of speed of sound.

 

[boneh3ad]

And also, I've looked into the speed of sound with regards to the temperature. The lower the temperature is, the faster the travel of speed of sound.

You made a mistake somewhere, then.

 

[Paulene Gueco]

Wait, what?

 

[boneh3ad]

The speed of sound in a gas that can be treated as a perfect gas (like air) has a well-known relationship with temperature, and it is not an inverse relationship.

 

[Paulene Gueco]

hmmmmmmmmmmmmmmmmmmmm

 

[boneh3ad]

For example: http://en.wikipedia.org/wiki/Speed_of_sound#Speed_in_ideal_gases_and_in_air

 

[Paulene Gueco]

Ohhh. That explains a lot. Thanks :)

Have you got suggestions on how I'd be able to do this experimentally as opposed to the one suggested above?

 

[boneh3ad]

I mean, there are any number of ways depending on what equipment you have available and how accurate you need to be. You could even do something simple like put a sound source and a pressure transducer/microphone in a foam-lined box (for acoustic insulation) a known distance apart and then record how long it takes for the microphone to register a sound you tell the source to make.

 

[sophiecentaur]

If you have a source of audio tones and a microphone, you can find the resonant frequencies of an open pipe, immersed vertically in a water bath (to change the temperature).
If you look at the formula in this link , you can see that the change over the temperature range obtainable in a water bath is not great so you may need to be careful with your measurements.
Google 'Open Pipe Resonance' for the background knowledge. Hyper physics is your friend in this sort of problem.

 

[Doug Huffman]

The box brings up a story. Sonar location needs an accurate measure of the speed of sound in water that has more parameters than in air. So a box is used with an ultrasonic transmitter and receiver timing the travel of pulses through water continually sampled by an auxiliary system. Some numbers from that part of my life; speed of sound in air is about 1000 fps, in water about 5000 fps and in steel about 15000 fps - as I recall.

 

[Danger]

speed of sound in air is about 1000 fps, in water about 5000 fps and in steel about 15000 fps

That suddenly made me think of something that never crossed my mind before. If something could manage to go fast enough under water, would there be a "sonic boom" similar to what happens in air? If so, how would it propagate?
The main reason that I'm curious about it is because of the still-untraced massively loud "booms" from underwater (somewhere in or near Asia, I think) that don't match any other known seismic signals. Maybe a small but extraordinarily powerful sea-floor volcanic eruption could spit out a rock that fast?

 

[jerromyjon]

would there be a "sonic boom" similar to what happens in air?

Very interesting thought! I don't think sound waves "pile up" in front of an object in water like they do in air. Perhaps they do, and if so it would seem to me the 1 to 5 ratio of the speed of sound in air vs. water would indicate the speed required would be mach 5! It seems like this might need its own thread...

 

[Danger]

the speed required would be mach 5

That's not quite the right way to phrase it, since the definition of Mach 1 is the speed of sound in a fluid. So it would technically still be Mach 1 even if it's 5 times faster than the speed of sound in air (and that is dependent upon air density at the time). I know what you mean, though.

 

[jerromyjon]

Oh thanks for the clarification, I've never even heard of mach in terms of fluid, but I do remember reading it varies with pressure/temperature.

 

[boneh3ad]

That suddenly made me think of something that never crossed my mind before. If something could manage to go fast enough under water, would there be a "sonic boom" similar to what happens in air? If so, how would it propagate?
The main reason that I'm curious about it is because of the still-untraced massively loud "booms" from underwater (somewhere in or near Asia, I think) that don't match any other known seismic signals. Maybe a small but extraordinarily powerful sea-floor volcanic eruption could spit out a rock that fast?

There would definitely be a shock wave in a situation such as that. Water is not really that different from air in terms of forming shocks other than the much greater speed required to do so. Otherwise, it is mathematically the same, requiring only a different equation of state if I recall. I don't know how the sound associated with the shock structure would be perceived underwater, though. I suppose it may be sonic-boom-like.

Oh thanks for the clarification, I've never even heard of mach in terms of fluid, but I do remember reading it varies with pressure/temperature.

Fluids are the primary context in which Mach number is used. Are you unclear about the difference between a fluid and a liquid (which is a type of fluid)?

 

[jerromyjon]

Are you unclear about the difference between a fluid and a liquid (which is a type of fluid)?

A liquid is a fluid, same as air is a fluid in many respects.

Technically all matter is fluid from my understanding.

 

[Doug Huffman]

A fluid deforms, shears, to occupy the available shape volume. A gas is a fluid that expands.

 

[sophiecentaur]

@ Danger: There must be many man made projectiles that travel at >Mach 5. That's all you would need.

 

[jerromyjon]

at >Mach 5.

My misunderstanding, mach 1 is the speed of sound in ANY given environment.

 

[Danger]

There must be many man made projectiles that travel at >Mach 5.

There are, but as far as I know they wouldn't have the "oomph" to make it through water at anything near that. As a much-slower example, a bullet from a .308 Winchester slows to the point that it won't injure someone within about 5 feet of entering water. I think that it's something like 8 feet for a .50 Barrett.
The only self-propelled things that I know of that can do Mach 5 are spacecraft , missiles, and some super-secret aeroplanes. None of those can even function under water, let alone overcome the extremely increased drag.

 

[nasu]

In water even Mach 1 is still to be realized. At least for man-made projectiles or submarines:
http://www.extremetech.com/extreme/...-in-100-minutes-creeps-ever-closer-to-reality

http://en.wikipedia.org/wiki/VA-111_Shkval

And it's not clear how will that count, as there is a bubble of gas around it.