[bprice2]

This kind of an "out-there" question I've been contemplating.  Does the air in my listening room have any affect on the sound I hear?  And, in particular, do humidity and air pressure have an affect on the bass produced by a ported speaker?

I ask, because (if I understand correctly) in a ported speaker bass is produced by way of air pressure building within the cabinet and then being pushed through the port when the pressure attains a certain level.  It seem to me that the "certain level" is dependent on conditions of the air in the listening room...like humidity and air pressure.

Am I applying false science in my contemplations?

[GHM]

Not at all..from talking to a very well known speaker designer and Physicist. The pressure does have an effect on the sound of a speaker. Even your elevation will effect the speakers response because of the air density and air pressure. I've heard this before...especially right before a weather front moves through the area.

[lonewolfny42]

I think there's a tweak for that....not sure if it works.... might need a bigger jar....

[GHM]

I think there's a tweak for that....not sure if it works.... might need a bigger jar....

  Chris you're a nut! Why didn't I think of that!

[jqp]

There is an effect on the sound due to pressure and humidity. How much is the question. If you are in a vacuum you would not hear sound...of course your eardrums would have burst. At the other extreme...

But I could imagine the sound would be different in a clearing in the rain forest than at he top of Mt Everest.

What could the effects be under the normal range of living conditions in a house? And what could you do to change conditions enough to notice?

[Srajan Ebaen]

I'm experimenting with the Franck Tchang Acoustic Resonators right now which are very potent in how they operate tho exactly how or why is hard to fathom. But never mind that. The point here is that the inventor's explanations started me thinking along certain lines that intersect with your question.

1/ The air in the room is in the signal path. Everything that's between the source and our ears (where sound is recognized *as* sound) is. Without the air molecules, the pressure waves generated by our speakers couldn't propagate. So the air is part of our system.
2/ Air is everywhere around us. Every air molecule is connected to every other one around the globe (except for rooms or containers that are literally airtight and sealed).
3/ When we close the doors to a room, it's not really a sealed container since there's leaks to the outside as is plain when you consider how much sound you can still hear outside the room.
4/ Especially in the lower corners behind the speakers but also the upper corners and then the corners behind the listening seat, there's zones of high pressure.
5/ If it's windy outside, there's high pressures exerting themselves also on what's inside the house (again, the only way to avoid that is to be hermetically sealed off.

In the "Franch View Of Things", unequal pressure distribution in a room causes negative acoustic effects and a lot of low-frequency pressure zones overdamp high frequencies to mask air, recorded ambience and micro detail. His devices -- don't ask me how -- "pierce" or "neutralize" these pressure zones as though, very basically speaking, someone drilled holes in the corners of your room to drain the pressure buildup outdoors. As you can imagine, that translates to sounding as though your room got wider. Plus, you can play louder without causing "room lock" and "overload". Bass gets better etc etc.

Once you start viewing the air in the room as an active element (it's elastic, it compresses) and realize that the air in the room connects with the air outside the room (unless yours is truly airtight), then it makes sense that pressure build-ups in this air will have an effect on the sonics. Altitude comes in as does humidity.

I don't mean to sound as though I really understood this stuff. I'm just starting to think along these lines to comprehend (attempt to comprehend) how these small resonators work. That they do is without doubt. And your question struck a nerve in that it looks at things from a similar angle, not necessarily having answers yet but at least starting to ask some interesting questions. 

So it's really not an out-there question. For sound to propagate, we need the air as carrier as it were...

[lonewolfny42]

Srajan Ebaen:

I'm experimenting with the Franck Tchang Acoustic Resonators right now which are very potent in how they operate tho exactly how or why is hard to fathom. But never mind that. The point here is that the inventor's explanations started me thinking along certain lines that intersect with your question.

Info link.... for further reading.....

[2bigears]

 a jar of the air from The Who concert a while back would work too,small doses of course.

[Daygloworange]

Have you ever noticed what cracking a window open in your car does to bass response when you are playing your car stereo? Sound travels further in water, and if memory serves me correct, much faster as well. I'm sure humidity has a definite effect. Air density must as well. Barometric pressure should have a definite effect.

I'm a guitar player. I've seen it happen over the years when we would isolate a Marshall speaker cabinet in a small sealed room for recording, that the pressure in the room would make the speaker cable blow out of the cabinet. ( The cabinet is a sealed box, and the speaker cable connection to the amp and cabinet is a phono plug.) We would have to duct tape the phono plug to hold it in there, or back off the screws on the input jack cup to relieve the pressure to prevent it from being pushed out. A 100 watt Marshall with the inputs bridged, cranked up, is about the loudest thing on earth, and moves a lot of air.

Great question. Air, air humidity level, air pressure, is an interesting topic of discussion.

Cheers

[zybar]

a jar of the air from The Who concert a while back would work too,small doses of course.

Now I know what I should sell on eBay next...   aa aa

How about some air from a Dead show circa 1969?   

Guaranteed to change the way you are hearing and seeing your system...

George

[Srajan Ebaen]

Hey, I don't mind levity at all. Otherwise things get far too serious. But there's something here that, I think, deserves some "seriousness", too.

For example -- and again in relation to these resonators which are on my mind right now -- people who have experimented with super tweeters out to 100kHz report on how it improves bass performance and focus. Sounds bizarre at first.

The resonators supposedly measure out to 3GHz. Who cares, you'd think, that's so far beyond our perception, it might as well not exist.
100kHz already is mighty out there and the only semi-plausible attempts at explaining the "audiblity" of super tweeters I've come across (from Tannoy for example) had to do with better phase fidelity in the audible band. Perhaps. Perhaps something else is going on that relies on infrasonics which we don't hear per se but whose side effects we do?

I'd sure love to see some "serious" attempts of chiming in on this broader topic, or some references to papers or research that point in the right direction.

Now back to the comedy channel. eats, shoots and leaves

See what an addition of a comma can do when referring to a panda? From Lynne Truss "The zero tolerance approach to punctuation"

[jqp]

For example -- and again in relation to these resonators which are on my mind right now -- people who have experimented with super tweeters out to 100kHz report on how it improves bass performance and focus. Sounds bizarre at first.

Here's an idea: the 100kHz waves "organize" the air and suspended water molecules with their tiny waveforms, which changes the medium for the bass waves

[Daygloworange]

As soon as a speaker starts to move, the sound pressure waves are in the realm of physics. There could well be a lot we haven't investigated in the realm of fluid dynamics, and aerodynamics as it pertains to audio.

I've had similar thoughts on the subject of super tweeters and what their potential effects might be on sound waves that are in the audible band. 

I'm sure that something like this could be easily modelled in CATIA.

Cheers

[Steve]

Hi bprice2,

Don't forget the temperature. From my understanding, 72 degrees was the standard. Did some experimenting and both below and above by only a couple of degrees can make a noticable difference.

Cheers

[rabpaul]

Hi,

The higher the density of a medium the faster the speed of sound travelling through it. So speed of sound is always faster in liquids and solids as compared to air. This also means at a given temperature sound will also travel faster in humid air. Sound also travels faster at higher temperatures as air is already in a faster state of motion. Higher pressure means higher density faster sound.

The question is can you hear a difference say in summer and winter? I live in the tropics so I can't answer this question. I do know that there is a difference with/without air-conditioning. I also think that a piece of music will sound best if you play at the temperature it was recorded in. I would think studios keep their temperature constant and have very little air moving in the recording area, in order to avoid moving air being picked up by the mics during a recording.

Wave theory suggests that you will get the average of two frequencies if you add a 20Khz wave to a 10Khz wave i.e a 15 Khz wave. So every frequency will benefit or be augmented by the addition of say a super-tweeter or at the other extreme a sub-woofer.(True/False)?

Rgds

[ctviggen]

Wave theory suggests that you will get the average of two frequencies if you add a 20Khz wave to a 10Khz wave i.e a 15 Khz wave.

I think all that happens is that you have a 20KHz wave and a 10KHz wave.  If you were to take a sampled time-domain version of this signal and transform it to the frequency domain, you'd see two spikes -- one a 20KHz and one at 10KHz.  What will generally happen, though, is you'll get harmonics at integer multiples of the frequency, such as 10K (1), 20k (2), 30k (3),....

I think if you look at the equations for room modes, for instance, these take into account the speed of sound.  The speed of sound is based mainly on pressure, such as if you're at a higher elevation, you need to reduce the speed of sound in the calculation.  The same thing would hold if you're in a high or low pressure area.

[elcaptain88]

Hi,

The higher the density of a medium the faster the speed of sound travelling through it. So speed of sound is always faster in liquids and solids as compared to air. This also means at a given temperature sound will also travel faster in humid air. Sound also travels faster at higher temperatures as air is already in a faster state of motion. Higher pressure means higher density faster sound.

This is not correct. Speed is a function of the square root of the ratio of stiffness (a coefficient) over density - so the generalization posted above may work in some comparisons but fails most. Increasing density actually reduces speed all other things being equal. Not too many engineers on this forum apparently.

[bprice2]

Well, this topic has been a whole lot more fun than I'd anticipated.  Thank you you all for your wonderful responses.  My original question was stated narrowly in regards to speaker function, however I now know and appreciate the fact that my stereo system is much larger than merely electronic components.  It consists of every air molecule in the world (to some degree).  Actually, this philosophy of interconnectedness reminds me of Jeff Golblum's explanation of the Chaos Theory in Jurassic Park...interesting.

Srajan, please keep us updated on the Resonators.  Honestly, I will have to re-read the article Chris posted, because I don't get it.  If there will be another testing of these devices in the central Texas area, I would love to participate.  If I was not an impoverished wannabee stereophile, I'd just plop down the money and try them out.  Oh well...so is life.

[PaulFolbrecht]

When I was chatting with Roy Johnson of Green Mountain Audio about his speakers, and appropriate amplifiers, he mentioned that he'd run the C3s with amps as low as 16W with absolutely no problems, and then noted that because I was in Milwaukee and he in Denver, my amp's power would actually go 30% or so farther due to the increased air pressure down here!  Holy cow, I thought, he's right!

I am a pilot (by hobby) and differences in air pressure due to elevation and weather effect everything we do to a great extent, so I should have thought of this effect in our hobby, but never had! 

Double-woo for living near sea-level!