Would you pay for something that you can't hear?

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#42
sam9 said:
Question for the physicists. Assume this device is actually pushing air at 1 GHz with an SPL comparable to an ordinary tweeter at 20kHz. What is the peak velocity of the air molecules? Consider the mass of the air being pushed, how many watts are required to acomplish this? (Assuming your amplifier is linear to 1GHz.) What will be the average temperature of the air molecules being pushed?

Extra credit: at what frequency will relativistic phenomona become a factor?
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Let's see... I'm not a physicist, but this should be right... it might be right... I hope:

The displacement of air molecules is proportional to the sound pressure and inversely proportional to the acoustic impedance and angular frequency, i.e.

d = p/(Zω)

Google says the acoustic impedance of air is 410 Nsm^-3 and sound pressure at 0dB is 2*10^-5 Pa.

hmmm... is it possible to do superscript on this forum?

Thus the displacement at 1GHz is 7.76*10^-18 m

The position of a molecules over time is given by x = d sin(ωt) which makes the velocity

v = dω cos(ωt)

Therefore the peak velocity is just dω or 48.8*10^-9 ms^-1 which is really, really slow, but it will of course be faster at higher SPL.

As for the power requirement: The air molecules must accelerate from 0 to peak velocity in 1/4 period, which means the power it needs is

P = 4/2 m v^2 / 1*10^9

Assuming the mass of an air molecule to be 4.8*10^-26kg (average of 29 atomic mass units per molecule) then that gives 228*10^-51 W.

Ok, that makes it look as though 1GHz sound waves are possible without violating any laws of physics. I suspect they wouldn't get very far before being absorbed though.
 
#43
Mr Evil said:

Ok, that makes it look as though 1GHz sound waves are possible without violating any laws of physics. I suspect they wouldn't get very far before being absorbed though.
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1GHz is considered a microwave frequency, they're good enough to get to the Clarke Belt at 22,500 miles and back, all to bring you re-runs of I Love Lucy. 🙂
 
#45
Um, guys,..for those in the US, I would check on the requirement of a FCC license. Don't run out and buy a pair just yet. They could end up costing a lot more than advertised as licensing is very expensive. Also, if someone in your hemisphere is already running a pair you will be turned down. Do your homework! :whazzat:
 
#47
mpmarino said:
Um, guys,..for those in the US, I would check on the requirement of a FCC license. Don't run out and buy a pair just yet. They could end up costing a lot more than advertised as licensing is very expensive. Also, if someone in your hemisphere is already running a pair you will be turned down. Do your homework! :whazzat:
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jacco vermeulen said:


Actually Jack, i think women's vocal cords already operate in the GHz range, half of what they're saying doesnt get through to me.
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1) There is a ham band in the 900MHZ range, and another at 1296MHz. -- you can operate on these bands with a Technician Class (no code) license.

2) "Whaddya say hunnnnyy ?" The problem is that you hear them at a critical juncture in a ball game, and you hear them just as you are downing your first cup of coffee, and you hear them snore.

Guess the only time a woman won't hear you 🙂
 
#51
Here's what I have to say....

Sound in the Megahertz are possible to produce but we lack the senses to percieve such a frequency. Gigahertz are just outrageous.

Air can only transmit sound to a certian high frequency. Beyond that the vibrations of the molecules become disorganized and random.
 
#52
BassAwdyO said:
Here's what I have to say....

Sound in the Megahertz are possible to produce but we lack the senses to percieve such a frequency. Gigahertz are just outrageous.
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The problem is, you just don't understand the science behind the Ultratweeter.

The Ultratweeter's main purpose is not the reproduction of gigahertz. The purpose of the Ultratweeter lies in the ancient science of separating the gullible from their money. 😉
 
#56
1) There is a ham band in the 900MHZ range, and another at 1296MHz. -- you can operate on these bands with a Technician Class (no code) license.
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ah, I was just kidding.

However, the fact that all that is spec'd is 'over 1 gig' would certainly put you into a territory that may/probably would require a license.:att'n:

My point is: If these things actually do what is claimed..they would likely be illegal..and could possibly 'roast' yer eyeballs. "over 1 gig" could mean anything!
 
#57
BassAwdyO said:
...Air can only transmit sound to a certian high frequency. Beyond that the vibrations of the molecules become disorganized and random.
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I know that air absorbs sound more as frequency increases, but I can't seem to find any numbers to go with that (the acoustic impedance of air I used in the previous caculations was all I could find, which is probably inapplicable at 1GHz). At some point, so much sound would be absorbed that it would be impossible to get any sound out of a speaker at all, but at what frequency?
 
#58
Carlos, I removed the posts with references to Bill's comments.

Here is the remainder of your post:


carlosfm wrote:

"The response on the super-tweeters (those that respond up to around 100khz) is very affected by room temperature and humidity.
The more distant is the listening posistion, the more roll-off of the very high frequencies, depending on the temperature and humidity.
Notice: measured, not listened.

It is hillarious to think about 1Ghz.

It's hot in here, I need a beer."
 
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