Can bass waves actually hurt you?

[jgsbass]

I went to a prestigeous science high school ( which will remain nameless for both our sakes) in the late 60's. My physics teacher who was a young guy, had just left a military lab job because they were developing sound weapons. The military were trying to figure out how to suspend subwoofers from helicopters without the rigging transmitting vibrations to the chopper( crashing the vehicle and killing the pilots along the way)
So, yeah i think its possible to inflict pain/damage with sound waves but I doubt that our equipment could kill someone ( unless it fell on them). I have experienced the uncomfortable feeling that comes from playing loud too close to a folded horn cabinet.

 

[scronus]

E.L.F. technoligeis are very real and some say dangerous to the human body .Have been known to cause confusion and feelings of parinoia and helplessness .Acoustic weapons are in use by our and european militaries .Not sure to what effect as most info is classified

 

[Kelly Lee]

[Mod hat on]Guys, let's keep it cool in here please.[/Mod hat off]

_________________________________________________

Im wating to see that 10db gain just by putting the mic in a car!

Being a former MECP certified mobile audio installer (10+ years removed) I can tell you that you do get a decibel gain from the enclosure provided by a vehicle. I can't remember the scientific reasons for this but I shall propose a little experiment for you. Pull your sub enclosure(s) from your vehicle and put them on the ground outside your vehicle while still being wired to your amps. Now, turn it on and retest your SPL level. It will be an enlightening experience.

 

[KeithPas]

E.L.F. technoligeis are very real and some say dangerous to the human body .Have been known to cause confusion and feelings of parinoia and helplessness .Acoustic weapons are in use by our and european militaries .Not sure to what effect as most info is classified

Confusion and paranoia yes, but still no "Brown Note". Hopefully some resourceful and creative sound engineer will figure that one out.

 

[billfitzmaurice]

The military were trying to figure out how to suspend subwoofers from helicopters without the rigging transmitting vibrations to the chopper

The hard part of it wasn't the rigging, it was the extension cords running back to the AC outlets on base.
Circa 1938 a bright Brit had the idea of aiming high-powered microwaves at enemy aircraft, literally cooking the aircrews inside. Upon testing it they found there wasn't enough power in the entire UK to provide adequate energy to make it work. It wasn't a total loss, they did invent radar and microwave ovens in the process.
The sillyness about the concept of destructive sound waves is due to sound waves having the same limitations as the Star Wars Defense and hand-held phasors: the power requirements are too high to make it practical. BTW, the loudest speaker system ever constructed was built by the DOD in an attempt to duplicate the levels of battlefield explosions, but without the explosions. All they ended up with was a lot of blown drivers. :scowl:

 

[billfitzmaurice]

I can tell you that you do get a decibel gain from the enclosure provided by a vehicle. I can't remember the scientific reasons for this

It's called Cabin Gain, which occurs at a rate of 12dB per octave beginning at the frequency which is 1/2 wavelength at the longest dimension of the enclosed space. But that's only one factor. Room resonant modes are also at work, so it's not at all unusual to see a 20 or even 30dB differential between the measured level inside the vehicle and that measured from outside the vehicle.

 

[emesen]

Back to my soundwave healing post from page one - the article I read was about 10-15 years ago, it might have been a Reeves Gabriel article from whatever Guitar mag he wrote his trippy articles for - they were way out there most of the time. You can go to http://www.harmonyera.com/ - it's kinda new age and the first site I found sort of summed up what I tried to say - not saying it's the best example, however at least I know I am not crazy and making things up

Whomever wrote "Low Frequencies cause G.A.S" - I damn near peed myself, that is so true.

 

[bongomania]

So Bill, did Kicker measure the spl of that van inside the cabin or outside the cabin?

 

[GCool]

I did not come in here to get in to a pissing match with ANYONE...
as well if it make you all feal better YOU ALL RIGHT and im all wrong..

Have a nice day!

 

[iamlowsound]

It's called Cabin Gain, which occurs at a rate of 12dB per octave beginning at the frequency which is 1/2 wavelength at the longest dimension of the enclosed space. But that's only one factor. Room resonant modes are also at work, so it's not at all unusual to see a 20 or even 30dB differential between the measured level inside the vehicle and that measured from outside the vehicle.

ANYONE competing in SPL competitions should know this. With this you can design a very loud system with much less power. Me and a friend had designed a system using this that we figured could hit 160db with around 20,000w. Unfortunately we did not have the money for this. A 20db loss with cabin gain when you are hitting 170db is still very impressive. I would love to get back into SPL competitions, but I just don't have the money.

BTW I designed a system that kicked out 140db at only 800wrms.

To answer the OP, I have seen people foolishly sit inside their cars while hitting 155+ and throwing up.

lowsound

 

[greenboy]

To answer the OP, I have seen people foolishly sit inside their cars while hitting 155+ and throwing up.

It's All About The Music, man ; }

 

[billfitzmaurice]

So Bill, did Kicker measure the spl of that van inside the cabin or outside the cabin?

Inside of course. Remember, they weren't just measuring the sound level, they were measuring the combination of the sound level and the elevated air pressure caused by the literal pumping up of the air inside the small enclosed space by the drivers. In fact, the reading shown on the meter would drop just by opening the windows. If you have access to a sound meter try this experiment: blow into it. Even with no sound present save that of your breath you can get a 130+dB reading. If someone wanted to cheat in an autosound competition all they'd have to do is turn on the windshield defroster.

 

[iamlowsound]

Inside of course. Remember, they weren't just measuring the sound level, they were measuring the combination of the sound level and the elevated air pressure caused by the literal pumping up of the air inside the small enclosed space by the drivers. In fact, the reading shown on the meter would drop just by opening the windows. If you have access to a sound meter try this experiment: blow into it. Even with no sound present save that of your breath you can get a 130+dB reading. If someone wanted to cheat in an autosound competition all they'd have to do is turn on the windshield defroster.

That is assuming that they are using a mic like that, which is rare these days. Also, the best way to hit massive numbers in a SPL competition is to pause the cd right before the peak of the note that you have determined is the optimum for your system, turn everything up as high as possible, back up, hit play. This is called burping your system (it sounds like a burp). The buildup of pressure would be negated here as there would be no build up, everything is done at low volumes until the actual burp.

lowsound

 

[billfitzmaurice]

That is assuming that they are using a mic like that, which is rare these days.

Whether it's a microphone or another device it's still measuring variations in air pressure, as that is how sound is transmitted through the atmosphere. No air= no sound, as in the vacuum of space.

 

[iamlowsound]

Whether it's a microphone or another device it's still measuring variations in air pressure, as that is how sound is transmitted through the atmosphere. No air= no sound, as in the vacuum of space.

True, but only the mics will register if you blow on them. The other thing that was talked about earlier wont. Do you have an explanation as to why "burping" a system produces more db than if you just ran that note without burping? I have always wanted to know, but haven't come up with an answer yet.

lowsound

 

[bobyoung53]

Inside of course. Remember, they weren't just measuring the sound level, they were measuring the combination of the sound level and the elevated air pressure caused by the literal pumping up of the air inside the small enclosed space by the drivers. In fact, the reading shown on the meter would drop just by opening the windows. If you have access to a sound meter try this experiment: blow into it. Even with no sound present save that of your breath you can get a 130+dB reading. If someone wanted to cheat in an autosound competition all they'd have to do is turn on the windshield defroster.

The sound pressure inside the van will go up and down depending on the frequency of the bass note being reproduced, when the drivers are pushed out the pressure raises, when they're sucked in it lowers, a 40 Hz tone does this 40 times per second. Sound waves create high and low pressure areas that would look like like dropping a rock in water, the frequency(s) you hear depends on how fast the waves hit your ear drum. I would imagine that a dB meter measures the difference between high and low air pressure. Of course if your windows are shut the air pressure on peaks will be higher and on lows will be lower than if the windows were open. This makes sense and the corollary is that the sound levels in the van will also be higher creating higher dB levels if the windows are shut. Cars also have vents which are always open which partially negates the open vs closed window theory anyway. I think GCool is right.

 

[bongomania]

Inside of course.

You miss my point- you weren't there, you don't know.

 

[bobyoung53]

It's called Cabin Gain, which occurs at a rate of 12dB per octave beginning at the frequency which is 1/2 wavelength at the longest dimension of the enclosed space. But that's only one factor. Room resonant modes are also at work, so it's not at all unusual to see a 20 or even 30dB differential between the measured level inside the vehicle and that measured from outside the vehicle.

http://www.caraudiohelp.com/newsletter/cabin_gain.htm

From the above link:

Have you ever wondered why car audio systems can have so much bass as compared to a home stereo system? The reason has to do with space. Your home has a lot of it and your car audio system doesn't. Because there is so little space in a car the bass notes (which are long waves) build up inside the passenger area. To calculate the length of a sound wave you divide the speed of sound (in feet per second) by the frequency. At sea level, the speed of sound is approximately 1,127 ft/sec. For example, a 40 Hz note has a wavelength of approximately 28 ft (at sea level).

(speed of sound)/(frequency) = wavelength

OR

(1,127 ft/sec)/(40Hz) = 28.175 ft

Since the length of the average car interior (including trunk) is in the 12 ft range the 40 Hz note will be longer then the car's interior. This is why notes below 70-90 Hz (depending on the vehicle) will have a greater output than the rest of the frequencies. Once this magic frequency is reached, bass output will increase by about 12 dB/octave below that frequency. This phenomenon is called cabin gain or "transfer function". So a smaller vehicle will have a greater cabin gain and should be able to have greater low bass than a larger vehicle. This is true for identical subwoofer systems with identical power. However larger vehicles are able to fit more subwoofers and amplifiers and so can out produce a smaller vehicle with limited space.

 

[bobyoung53]

You miss my point- you weren't there, you don't know.

I got it, of course sound (SPL) inside a car is going to be louder than the same equipment in the middle of a football field.

 

[GCool]

ANYONE competing in SPL competitions should know this. With this you can design a very loud system with much less power. Me and a friend had designed a system using this that we figured could hit 160db with around 20,000w. Unfortunately we did not have the money for this. A 20db loss with cabin gain when you are hitting 170db is still very impressive. I would love to get back into SPL competitions, but I just don't have the money.

BTW I designed a system that kicked out 140db at only 800wrms.

To answer the OP, I have seen people foolishly sit inside their cars while hitting 155+ and throwing up.

lowsound

Last year I was running 4 4,000 watt amps to hit a 156.0. With the impedance rise and the resident frequency for my car I was only able to get a little over 10k. I know this by testing every burp with a current clamp and a D.V.M. By taking Aac x Acv you receive your wattage by dividing the 2 numbers you get the impedance you received you wattage.