I think the record for the highest continuous sound pressure in a car is 156dB.
A jet plane at full power 50m away is 140dB.
An airbag deployment in a car is a pop of 160dB.
The explosion from a heavy weapon at 10m is 170dB.

Sound pressure is measured on a logarithmic scale so each added 10dB is 10 times the pressure.

I think air cavitates at a continuous sound pressure of 160dB which is the max continuous sound pressure possible.

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AT 369lbs. who cares about a few extra ounces between copper vs. aluminum?? Copper makes for better heat transfer than aluminum also.

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@HiTech

I am not much into loud audio, but figured a lighter coil might allow the cone to accelerate better.

Here is a relevant patent:

http://www.freepatentsonline.com/3935402.html

Here is a quote from a speaker manufacturer that supports use of aluminum. Apparently it is used of 3 reasons:

1) Increased current capacity and heat dissipation
2) Anodized aluminum can get hotter than enameled copper without hurting the insulation
3) Low mass

John

 

The maximum sound pressure level is 191dB.
http://en.wikipedia.org/wiki/Sound#E...ressure_levels

This is because at this level the compression is >2 times amptmospheric pressure and the rarefaction is a vacuum.

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Thanks, Hero.
The max continuous sound pressure in air is pretty high.

I calculated that a single Jackhammer subwoofer produces 130dB at 1m with an input of 6000W continuously.

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@Hero999

But if the sound is distorted, presumably the spl can go higher. Anyway, thanks for the clarification. I was lazy and didn't bother to look it up.

I guess you just can't believe everything a teenager tells you.

John

 

That's true but once you get past atmospheric pressure, the characteristics of the wave change so it's no longer called a soundwave but a shockwave.

Have you seen a high speed video of a large bomb exploding? You can actually see the shock wave as the light is refracted more by high pressure air.

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Absolutely, but where is the boundary between shock and sound for these kids' cars? At first, I thought the refractive aberrations were just schlieren lines from the heat. Now, with even more powerful systems, I suspect they are shock waves.

BTW, you get a similar effect from the leading edge of high-speed jet aircraft, which allows one to actually see a little past the leading edge under the flight path.

 

Technically the boundry between shock and sound waves is clearly defined at 191dBA.

However, can probably see sound at lower pressure levels than shockwaves as any pressure change will alter the refractive index of air. I wonder if there's a way to amplify this effect so we can see lower level sounds at low frequencies. I haven't given this much thought.

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@Hero999
I bought a sound "laser" kit (makes coherent sound) from the Pennsylvania State University acoustics department. Produces low frequency sound/pressure waves that can blow out a candle at several inches. Intent is to experiment with a directed counter measure. But, no time yet to play with it. John

 

I think that the monster Jackhammer 22" 6000W sub-woofer can blow out a candle a meter away. Its cone moves 5 inches peak-to-peak.

Some of the powerful PRO subwoofers I worked with could nearly break your leg with the air coming from the port.

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No wonder the people who have them in their cars don't seem too bright.

Yes, use of sound as a weapon dates way back. John

 

That is the object: breaking glass.
To cruise thru the hood and pop the windows.
Our gov is just class selective enough to make it effectively not illegal.

 

You revive a thread from July to give us that jewel?

What class of idiots do you feel is being discriminated against?

John

 

Oh I could put that to good use in a car!

Do you know what you get when you put a single impulse into that thing and chanel it through a pipe?

A sonic canon to burst offenders' autoglass A single huge pulse. The other possability is HP directed ultrasonics.