Transient response correlated to temperature?

Posted: Tue May 16, 2006 9:38 pm

Ok so the speed of sound at 70 degrees F at sea level is aprox 1130 feet per second. Now the speed of sound at 0 degrees F is 1051 feet per second according to

http://hyperphysics.phy-astr.gsu.edu/HBASE/sound/souspe.html

Would you notice a change in your recordings if they where done at these two different temperatures in playback? Assuming you were playing back at a temperature different from those that where recorded in. How would the transient response be between the two? Would the recordings done at higher temperatures have crisper transient response? Would there be a notable difference? I imagine that there is a difference in sound just not sure as to how much. Thanks in advance. Very Happy

Posted: Tue May 16, 2006 10:22 pm

Well, you would think that reverberation in a church would be longer in the wintertime when the air is driest, and shorter in the summertime when the humidity is highest and the air heavier? But it's not, it's just the opposite so I think it would be a good idea for all symphony orchestras to play in subfreezing temperatures so that everything sounds better??? I mean that way the instruments wouldn't go sharp when you play them a lot?? So does driving at 50 mph really save gas or does it just seem that way because it took you longer to get to where you wanted to go? Maybe that is why rich people pay less in taxes??

Everything you know is wrong!
We are all bozos on this bus!
Hey man, don't answer the phone, I think it's bugged?
Ms. Remy Fire Chong

Posted: Wed May 17, 2006 12:25 pm

RemyRAD wrote:

Well, you would think that reverberation in a church would be longer in the wintertime when the air is driest, and shorter in the summertime when the humidity is highest and the air heavier? But it's not, it's just the opposite so I think it would be a good idea for all symphony orchestras to play in subfreezing temperatures so that everything sounds better??? I mean that way the instruments wouldn't go sharp when you play them a lot?? So does driving at 50 mph really save gas or does it just seem that way because it took you longer to get to where you wanted to go? Maybe that is why rich people pay less in taxes??

Liquid Temperature (°C) Speed in m/s
Water 0 1402
Water 20 1482
Methyl alcohol 0 1130
Sea water
3.5% salinity 20 1522

Temperature measurement from sound speeds

Perhaps the humidity in the air of the church is causing the sound to move faster causing more reverberation since the speed of sound in water is about 4600 feet per second (1402 meters per second) vs 1130 feet per second.

In Sub freezing temps sound would move slower(depending on humidity). There are many variables to consider and the perfect world in physics is hard to come by. But the concepts are interesting. I don't know if any of this will have a correlation as to how one would or will record in the grand scheme of things but I find these conceptes interesting and perhaps they may be useful in the future.

I remember reading that a band was recorded underwater in the guiness book of world records a long time ago. I wont be soaking any microphones in a pool or my acoustic guitar for that matter but I find it odd yet interesting that people are trying new things.

As to driving 50 mph do people still drive that slow to work? Laughing

And taxes well thats another issue. Mr. Green

Posted: Wed May 17, 2006 1:07 pm

In large rooms the reverberation time in function of air, is influenced by 2 main factors.

1) The speed of sound mainly defined by Temperature (there are much more complicated models taking more parameters into account, but their significance is minor)

2) The absorption of sound in air, and that's much more complicated already.
This is mainly related with Pressure, Temperature and Humidity.
This point 2 is a rather complex thing.
The most accurate approach of this is described in ISO 9613-1, but that's a series of long complicated formulas.

Correct is that it is possible to measure e.g. the Reverberation Time in an unheated, cold, still moisty hall at bad weather, just finished or something and recalculate this reverberation time to standard Relative Humidity, pressure and temperature conditions.

This is no theory but practical reality, of course with some uncertainties and tolerances always existing, and assuming that the interior is not completely changed by furniture and so on.

You can hear the difference in the acoustics of a hall in such deviating conditions. (not with minor deviations of cource).
Hence since the RT is frequency dependent (non-linear) different which can be surprisingly audible, I assume it has an impact on recording also.

Best regards
Eric

Posted: Wed May 17, 2006 2:07 pm

BigAL wrote:

...As to driving 50 mph do people still drive that slow to work? ....

She's from NOVA. People up there dream of driving 50mph. (Usually while their sleeping in a traffic jam or while driving at 90mph to get to the next jam.)

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