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# Do you notice that sound is faster in the morning? - Page 4

Lol, I remember some guy recommending coming your AT M50 in the freezer over the night, and the sound becomes much tighter for a week or two. Try putting your headphones in the freezer

In my experience volume levels increase exponentially with the intake of alcohol. But still, I seem to have read somewhere that your ears actually become more sensitive from alcohol. Dunno..

Quote:
Originally Posted by davidsh

Lol, I remember some guy recommending coming your AT M50 in the freezer over the night, and the sound becomes much tighter for a week or two. Try putting your headphones in the freezer

I would think that would tend to embrittle the plastic and lead to breaking the headband and other parts.

We need to put to rest this "speed of sound vs temperature" thing.

First, the speed of sound and temperature are related, but not in the way that's mostly been posted here.  Sound slows down in cooler air.

Here are two references, calculators you can play with:

http://www.sengpielaudio.com/calculator-speedsound.htm

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

So, just to be clear, sound does not speed up in colder air, it slows down.

However, when we're talking about headphones, it doesn't matter, not one tiny bit.  Here's why:

If the speed of sound at 70F/21.1C is 1129.52ft/second, and the speed of sound at 60F/20C is 1118.40ft/sec, then for a 10 degree F drop in temperature we have a 1% change in speed.  What does that do to the arrival time of sound from a headphone to the eardrum?

Assuming the distance from a headphone driver to an eardrum is 1.25" (just an assumption), then at 70F the time it takes for sound to transition 1.25" is 73.7uS .  For the same distance at 60F, it takes 74.5uS.  If we convert that time to an equivalent change in distance at 70F, the 10 degree temp change is like moving the transducer 0.010" further away from your eardrum.  Yes, 10 thousandths of an inch.  That's for headphones, for IEMs the difference is even smaller, by something like half.  By the way, the air temperature between an IEM and the eardrum has nothing to do with ambient air, it's pretty much body heat, somewhere around 98.6 unless you're sick.  It's also pretty stable unless you are out in very very cold air.

Ok, so let's not keep puzzling over the effect of temperature on the speed of sound as it relates to headphones and IEMs.

edit: my usual spelling errors

Edited by jaddie - 8/11/13 at 1:43pm
Quote:

We need to put to rest this "speed of sound vs temperature" thing.

First, the speed of sound and temperature are related, but not in the way that's mostly been posted here.  Sound slows down in cooler air.

Here are two references, calculators you can play with:

http://www.sengpielaudio.com/calculator-speedsound.htm

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

So, just to be clear, sound does not speed up in colder air, it slows down.

However, when we're talking about headphones, it doesn't matter, not one tiny bit.  Here's why:

If the speed of sound at 70F/21.1C is 1129.52ft/second, and the speed of sound at 60F/20C is 1118.40ft/sec, then for a 10 degree F drop in temperature we have a 1% change in speed.  What does that do to the arrival time of sound from a headphone to the eardrum?

Assuming the distance from a headphone driver to an eardrum is 1.25" (just an assumption), then at 70F the time it takes for sound to transition 1.25" is 73.7uS .  For the same distance at 60F, it takes 74.5uS.  If we convert that time to an equivalent change in distance at 70F, the 10 degree temp change is like moving the transducer 0.010" further away from your eardrum.  Yes, 10 thousandths of an inch.  That's for headphones, for IEMs the difference is even smaller, by something like half.  By the way, the air temperature between an IEM and the eardrum has nothing to do with ambient air, it's pretty much body heat, somewhere around 98.6 unless you're sick.  It's also pretty stable unless you are out in very very cold air.

Ok, so let's not keep puzzling over the effect of temperature on the speed of sound as it relates to headphones and IEMs.

edit: my usual spelling errors

Interesting post, but I think we are in agreement that this is the key statement that caused your response:

Quote:
It's also an absolute fact that the gas laws dictate that colder air is denser (PV=nRT), thus - sound travels faster in colder air.

This is wrong and we put it to rest a couple of pages ago.  It's not that colder is denser - that IS a fact, but the fact that sound travels faster in denser air is NOT.  I admitted that I was wrong in assuming this a couple of pages ago.

The problem is that air - even when denser - is still compressible (allows pressure changes).  That makes all the difference in the world and that difference doesn't exist for liquid and solid media.  Because of that, sound must travel through air molecules in a compression wave - fast enough, and it becomes a shock wave.  All the while, energy is wasted through more molecules because it's dissipated from compressing the space and increasing the pressure (energy) between those molecules.  I admitted as much a couple of pages ago.

Meanwhile, as to the rest of it - no offense - but you make a huge assumption that the ear can't hear differences that you cite.  It may seem crazily minute, but you cite no proof that the ear can't tell the difference.  For example, the armatures in IEM's are almost macroscopic in transducing sound, but we hear the differences quite clearly.

Quote:
Originally Posted by tomb

Meanwhile, as to the rest of it - no offense - but you make a huge assumption that the ear can't hear differences that you cite.  It may seem crazily minute, but you cite no proof that the ear can't tell the difference.  For example, the armatures in IEM's are almost macroscopic in transducing sound, but we hear the differences quite clearly.

Not a huge assumption, though.  Broadband time delay is inaudible.  If all frequencies are delayed an equal amount of time, you have no group delay issues.  The only time delay becomes audible is when the time delay is non-linear over frequency. Changing the broadband time delay by 1% would be inaudible.  You aren't changing the position of the transducer relative to the ear (that would possibly be audible), you aren't changing the frequencies of any possible audible resonances by enough to be audible either.

As to proof, I recognize your desire for cited references, and that's a reasonable request most of the time.  However, in this case, the proof can easily be seen empirically.

Lets set the conditions first.  A 10 degree F temperature change over the course of a day is, in a temperature controlled space, rather unusual, would be considered uncomfortable, but lets assume our space is only partially temperature controlled and go with a 10 degree F change.  Our concern, however, is not with the ambient temperature, but with the temperature of the air as a transmission medium between the transducer and the eardrum.  The air in that path is only partially influenced by the ambient temperature, as for IEMs, the ear canal is sealed, and can be assumed be be at body temperature all the time, except perhaps in the case of extremes.  Our 10 degree ambient change becomes moot, because it doesn't exist in the canal.  For circumnaural headphones, there is also air heating, perhaps to a lesser extent, but anyone who wears full size headphones knows they get hot.  On-ear, or "open-air" headphones may possibly be the most easily influenced by ambient changes, but even in that case, the greater percentage of the air in the transmission path is within the ear canal, and is therefore heated.  The balance of the air between the outer ear and the transducer will also be heated, but to a lesser extent.  It would be reasonable to assume the ambient temperature change in our conditions would be reflected in that space to the extent of 20 - 30% of the total ambient change.

Now recall that if we had a transmission path length of 1.25", and that total path changed 10 degrees, we'd have a 1% broadband time delay change.  If we have body-heated air, now, changing only by 30% of the total change, we now have a total time delay change of about .3%, assuming the entire transmission length changes, which it won't.  I would be reasonable to assume that even with open-air headphones, a 10 degree ambient change would result in a .2% change in the transmission air path related time delay.

So, what would be audible about that?  One possibility would be re-tuning of a first-order resonance, perhaps mode set up between the ear drum and the transducer.  For a path length, admittedly assumed, of 1.25 inches, that mode would occur at 10,850Hz, a frequency at which we have very ability to discern frequency accurately.  A .2% change would result in a retuning of that mode to 10828.3, which is a change too small to be detectable at that frequency.  I'll leave the calculation of that deviation in cents to someone else.

Citing the macroscopic differences in the armatures in IEM's is irrelevant to this discussion, as that mechanism is entirely different in nature, and yes, they are clearly audible.

Now if we want to talk about how temperature affects a transducer, that's fine, might be audible, and could be tested.  But again, the effect of a 10 degree ambient change is inaudible, as can be seen, again, empirically.

Quote:
<snip>

Citing the macroscopic differences in the armatures in IEM's is irrelevant to this discussion, as that mechanism is entirely different in nature, and yes, they are clearly audible.

</snip>

Interesting interpretation, but I suggest again that you're making a whale of a lot of assumptions.  You're completely ignoring the material effects of the transducer itself from temperature, that's why I cited the example of IEM armatures.  Granted, that's not what was being discussed up to now with the speed of sound in air relative to temperature.  However - I don't think your assertions can be classified as empiricism.  It would be empirical if you measured the frequency response at different temperatures and different frequencies of different transducers.  That's not what you're posting here - only an extrapolation based on assumptions of the other variables with respect to the speed of sound in air.  I stated that there's no argument with that.

Needless to say, this has gone way beyond the OP's original question and is probably more suited to the Sound Science forum section.

P.S. In one respect, it's a good education for a newbie of what happens with esoteric questions presented to a group of audiophiles.

If temperature is a factor, who sleeps in freezing cold conditions, sure the house has a thermostat or temperature control, so the difference in a few degrees won’t do much. Like I said before, I think it’s more to do with not using “your ears” while you sleep, similar to your eyes when you wake up, very sensitive to changes. I do find that sound is more “crisp” in the morning, even people talking, but this changes within a few minutes. In the end, every man to himself.

Quote:
Originally Posted by tomb

Interesting interpretation, but I suggest again that you're making a whale of a lot of assumptions.

I'm making one assumption: the distance from the transducer to the ear drum.  All other "assumptions", as you call them, are just physics. You are free to disagree with them.

Quote:
Originally Posted by tomb

You're completely ignoring the material effects of the transducer itself from temperature, that's why I cited the example of IEM armatures.  Granted, that's not what was being discussed up to now with the speed of sound in air relative to temperature.  However - I don't think your assertions can be classified as empiricism.  It would be empirical if you measured the frequency response at different temperatures and different frequencies of different transducers.  That's not what you're posting here - only an extrapolation based on assumptions of the other variables with respect to the speed of sound in air.  I stated that there's no argument with that.

Yes, you are correct, I'm completely ignoring the material effects of the transducer itself from temperature, and that's NOT what was being talked about.  I would suggest that given the rather narrow temperature range it has to normally operate in, however, it's doubtful 10 degrees ambient change makes any difference either, but that's only my guess, not fact.  I don't need to measure frequency response at different temperatures and different transducers because that's not what I'm talking about.   My conclusions are precisely empirical because speed of sound through air is well known, as are how temperature affects it.  My conclusions are simply calculations based on known parameters and one assumption: the distance from the transducer to the ear drum.

But as I showed, it doesn't matter anyway.  10 degrees change in ambient will not result in 10 degrees change within the ear.  I'm not extrapolating anything, I have only one variable, and it's arguably moot.

Quote:
Originally Posted by tomb
Needless to say, this has gone way beyond the OP's original question and is probably more suited to the Sound Science forum section.

P.S. In one respect, it's a good education for a newbie of what happens with esoteric questions presented to a group of audiophiles.

Somewhere back in this thread it was asserted that there was an audible change due to the cooler air temperature in the morning, and that was coupled with the assertion that the change is because sound travels faster in cooler air.  That's the issue I'm addressing.  Ambient air temperature has nothing to do with the so-called, and BTW unsubstantiated, audible change.  Sound travels slower in cooler air (sorry, that's a fact), the air in the ear is heated to near body temperature (easily proven, but I don't think it worth the time at this point), and doesn't track ambient air temperature change.  There's also too little of it (air) in the system to matter anyway.

I only responded because nobody seemed to understand the physics...or perhaps care to.

If I've offended anyone by bringing science into the discussion, I apologize profusely.  Everyone is welcome to find their favorite myth and hang on tight.   Everyone here is free to believe that the speed of sound goes up or down in cooler air, and that it has a huge audible effect. I tend to reach for reality, but if that's not your thing, grab whatever you want.

I'll take this opportunity to apologize to the audiophiles too.  I'm not one in the classic sense, as you can tell.  Sorry guys, have fun, carry on.

Quote:

I'm making one assumption: the distance from the transducer to the ear drum.  All other "assumptions", as you call them, are just physics. You are free to disagree with them.

Yes, you are correct, I'm completely ignoring the material effects of the transducer itself from temperature, and that's NOT what was being talked about.  I would suggest that given the rather narrow temperature range it has to normally operate in, however, it's doubtful 10 degrees ambient change makes any difference either, but that's only my guess, not fact.  I don't need to measure frequency response at different temperatures and different transducers because that's not what I'm talking about.   My conclusions are precisely empirical because speed of sound through air is well known, as are how temperature affects it.  My conclusions are simply calculations based on known parameters and one assumption: the distance from the transducer to the ear drum.

But as I showed, it doesn't matter anyway.  10 degrees change in ambient will not result in 10 degrees change within the ear.  I'm not extrapolating anything, I have only one variable, and it's arguably moot.
Somewhere back in this thread it was asserted that there was an audible change due to the cooler air temperature in the morning, and that was coupled with the assertion that the change is because sound travels faster in cooler air.  That's the issue I'm addressing.  Ambient air temperature has nothing to do with the so-called, and BTW unsubstantiated, audible change.  Sound travels slower in cooler air (sorry, that's a fact), the air in the ear is heated to near body temperature (easily proven, but I don't think it worth the time at this point), and doesn't track ambient air temperature change.  There's also too little of it (air) in the system to matter anyway.

I only responded because nobody seemed to understand the physics...or perhaps care to.

If I've offended anyone by bringing science into the discussion, I apologize profusely.  Everyone is welcome to find their favorite myth and hang on tight.   Everyone here is free to believe that the speed of sound goes up or down in cooler air, and that it has a huge audible effect. I tend to reach for reality, but if that's not your thing, grab whatever you want.

I'll take this opportunity to apologize to the audiophiles too.  I'm not one in the classic sense, as you can tell.  Sorry guys, have fun, carry on.

It doesn't matter who you offend because you are in my thread and I'm cool with the enlightenment.
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