Armed Polite Society
Main Forums => The Roundtable => Topic started by: zahc on September 13, 2009, 02:02:54 AM
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UV can damage your eyes. As far as I know, IR cannot.
So, can ultrasound damage your hearing if you can't hear it, in other words, is decibels all that matters? Lumens certainly isn't all that matters in vision, because of the UV thing. I'm trying to figure out if heterodyning two kW range ultrasound transducers 20-100hz apart (for stirring coffee beans while home-roasting, of course) would damage your hearing.
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Think of your ear drums as tuning forks. They get excited by certain frequencies but not by others. Ultrasonic frequencies are so many octaves above the natural frequencies of your ear drums that there's basically no exitation. That's why you can't hear it. With no exitation, there's no damage (well, unless you crank up the dB's to dangerous levels, but 2kW probably isn't capable of that). Even if you did do damage it would be to a range that you have no hearing for anyway.
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When my wife was pregnant i was always hesitant about her getting an ultrasound, as i questioned it being damaging to a developing fetus. I never did find any articles to support my fears.
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I think ultrasound might be damaging when it is so loud that it causes physical harm (sound is just a wave of air of different densities). So unless you will encounter 120 decibel of ultrasound there sound be no danger.
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I want to hear more about the coffee roasting.
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So unless you will encounter 120 decibel of ultrasound there sound be no danger.
The thing is, I think that 120 decibels of ultrasound is impossible, because the determination of decibels is based on the sensitivity of the ear. If the sensitivity of the ear is zero at a certain frequency, then you will always have zero decibels regardless of the actual power of the sound. Similarly, you can never have 1 lumen of IR or UV, no matter how "bright" they are, because the definition of lumen is weighted to human vision in a similar way.
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This may help. (http://www.hc-sc.gc.ca/ewh-semt/pubs/radiation/safety-code_24-securite/health-sante-eng.php)
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The thing is, I think that 120 decibels of ultrasound is impossible, because the determination of decibels is based on the sensitivity of the ear. If the sensitivity of the ear is zero at a certain frequency, then you will always have zero decibels regardless of the actual power of the sound. Similarly, you can never have 1 lumen of IR or UV, no matter how "bright" they are, because the definition of lumen is weighted to human vision in a similar way.
No, I think you are confusing Sone with Decibel. the article Allanea posted mentions dB of ultrasound as well.
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UV can damage your eyes. As far as I know, IR cannot.
I suspect that if you got your eyeball in front of an IR laser of sufficient wattage, you'd find out diffrently.
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Isn't IR essentially heat?
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When my wife was pregnant i was always hesitant about her getting an ultrasound, as i questioned it being damaging to a developing fetus. I never did find any articles to support my fears.
There are a few out there, but the suspected adverse effects are linked to slight increases in temperature rather than any specific threat to hearing. It's the usual concerns--subtle neurological problems that may or may not exist and that may or may not be linked to ultrasound or any one of a dozens of things we've added to our lives the past couple of generations.
I was always more worried about noise from shooting than "noise" from ultrasound.
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Isn't IR essentially heat?
IR is converted to heat on hitting a reactive surface, like flesh. Even relatively low-power IR lasers, if pulsed at a sufficiently brief pulse length and high enough PRF can severely damage eye tissue.
TC
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Visible light is composed of electromagnetic radiation of wavelengths ranging from about 0.39 microns (violet) to 0.78 microns (deep red.) UV light has wavelengths shorter than 0.39 microns and IR light has wavelengths longer than 0.78 microns. Both UV and IR can be damaging, with the type of damage depending on wavelength. For example, light from an Nd:YAG laser at 1.06 microns is EXTREMELY hazardous to the retina, as the lens and cornea are transparent to it and will focus it - even diffusely scattered light from a sufficiently powerful Nd:YAG is hazardous. On the other hand, light from a CO2 laser at 10.6 microns is stopped by the cornea, and diffusely scattered light from one of these lasers with even moderate power has little eye hazard - but considering that CO2 lasers are used to cut metal, acrylic, etc., you better be careful to avoid direct exposure to the beam itself, depending on the actual power of the laser.
As for ultrasonics . . . I've no doubt that at sufficient power levels, they'd be bad for you. But I've no idea what those power levels are.