Brain Teasers
Joe Thunder
As his name would suggest, Joe was not a meek, quiet fellow. In fact he had such difficulty keeping quiet, both his local and university library banned him. His roommate, being a music major and a sound engineer, said he could solve his problem, but Joe would need to trust him. He gave Joe his 75-watt ghetto blaster, a CD, fake mustache, and a long blond wig. Joe, who is sceptical but intrigued, decided to give it a shot. Joe, disguised as one of the professors, entered the university library. He placed the CD player on the table in front of him; loaded the CD; cranked the volume full and braced himself as he turned it on. Surprisingly there was only a very very faint sshh. Joe then realized that he couldn't hear anything at all. He spoke normally, and then yelled, but no one reacted. Awesome, he thought as he began flailing his arms around and shouting as loud as he could. Unfortunately, the librarian, seeing him moving but hearing nothing, assumed he was choking and performed the Heimlich maneuver on him, knocking his wig off, causing the librarian to perform the hind kick maneuver right out the door. Poor Joe.
But what had his roommate done? What was on that mysterious CD that made everything quiet?
But what had his roommate done? What was on that mysterious CD that made everything quiet?
Hint
Think sound and what people can and can't hear.Answer
Most airline pilots could tell you. Joe's roommate used the same technology that airline and fighter pilots have in their noise cancelling headsets. It works like this; the CD had a low frequency sound (below the 20 Hz which humans can't hear) recorded on it. As long as the volume of the low frequency is louder than your voice or other noise, you hear almost nothing for the low sounds (which humans can't hear) and drown out other sounds. I heard that when this was first discovered that libraries actually used this concept to create quiet until they realized that even though humans couldn't hear the low sound, if loud enough, it would still damage the ears.Hide Hint Show Hint Hide Answer Show Answer
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Comments
Mar 26, 2003
Hehe... hind kick maneuver... that's funny :-)
cool teaser
Hear Ye! Hear Ye ! a good informative teaser. More
Sounds good to me.
I like this one. In fact, I was going to do a teaser with a similar concept, but I won't know. It was done nicely here!
Erm...one problem with this teaser. Mr. Thunder would have to have a very, very good CD player in order for this to work. Manufacturers tend to build stereo equipment that only responds to the human aural response range (in order to filter out unwanted electrical impulses and suchlike) - hence the low-frequency sound on the CD would not make it past all but the very best speakers.
i don't get it....
rad I love your teasers
i figured out the waves canceling part but not the specifics
Wow! I totally did NOT get that one, but I learned a lot! Awesome!
How interesting. I like these science teasers; I learn neat facts from them!
I did not know that, very cool
Cool little fact, but very poorly written to tell the truth. I had a hard time deciphering the riddle due to the lack of proper punctuation and such. More of a trivia question than a riddle or puzzle really, as it took actual knowledge of the technology rather than problem-solving skills to figure it out.
cool teaser. actually rhettfairy, this is not truley a riddle. its a science riddle which is like trivia only....science although you probably did have to be a science whiz to know that one! that was very interseting and i learned something new.
Wow..... I found this one to be absolutely fascinating!!! I had no idea there was "sound cancelling" technology!! Makes me wonder if the "principle" demonstrated here explains why a person with a mild to moderate hearing loss has more trouble understanding speech when there is background noise. I know that most consonant sounds in human speech are in the higher frequency range. Assuming that the background noise is of a lower frequency, but still audible.... would the background noise actually cancel out the higher pitched sounds, and thus make it difficult for one to understand conversation? Any scientists out there that know the answer to this?
i knew this one .
some guy let me use his bose headphones on the plane .
some guy let me use his bose headphones on the plane .
Excellent, I hadn't heard of that before (no pun intended).
I can't believe someone complaining about the punctuation. Maybe they had PERIOD pains or need to undergo COLONic irrigation .
I can't believe someone complaining about the punctuation. Maybe they had PERIOD pains or need to undergo COLONic irrigation .
Bose use a different technology...
look up Noise cancelling headphone in Wikipedia (link not allowed here since it has >50 letters)
look up Noise cancelling headphone in Wikipedia (link not allowed here since it has >50 letters)
Here is a link to the Wikipedia article about how noise cancellation actually works. http://tinyurl.com/2ebor6
Joe's boombox would have to be very advanced indeed.
Joe's boombox would have to be very advanced indeed.
This is utterly nonsensical.
The phenomenon demonstrated here is as fictitious as Joe Thunder.
Active Noise Cancellation doesn't work by playing random infrasounds as said here. It produces sound patterns identical to ambient noise, inverted. So the two (Noise and Anti-Noise) cancel out in the ear.
The idea of an inaudible sound "drowning" other sounds simply because it's more intense (not LOUDer, loudness concerns audible sounds) is against the Principle of Superposition.
The phenomenon demonstrated here is as fictitious as Joe Thunder.
Active Noise Cancellation doesn't work by playing random infrasounds as said here. It produces sound patterns identical to ambient noise, inverted. So the two (Noise and Anti-Noise) cancel out in the ear.
The idea of an inaudible sound "drowning" other sounds simply because it's more intense (not LOUDer, loudness concerns audible sounds) is against the Principle of Superposition.
Feb 06, 2011
This is not how sound cancellation works. The author has confused masking with sound cancellation. Masking works by playing a sound loud enough to render another sound inaudible. Sound cancellation works by creating another sound with 180 degree phase shift to reduce the amplitude of the first sound.
An inaudible sound cannot be "louder" than an audible sound and an inaudible sound cannot mask an audible sound.
An inaudible sound cannot be "louder" than an audible sound and an inaudible sound cannot mask an audible sound.
That is AWESOME!!! I don't care what all those comments said, it's still one of the coolest things I've ever heard of. I wish there was, like, a YouTube video that recorded that sound, then I would play it and talk. AWESOME!!
That is AWESOME!!! I don't care what all those comments said, it's still one of the coolest things I've ever heard of. I wish there was, like, a YouTube video that recorded that sound, then I would play it and talk. AWESOME!!
Bunk.
Not how noise cancelling headphones work. Think about it... you can't see a computer screen outside because there is too much visible light drowning it out. This riddle suggestes you wouldn't be able to see a computer screen when there is too much radio frequency light around. It makes no sense.
Not how noise cancelling headphones work. Think about it... you can't see a computer screen outside because there is too much visible light drowning it out. This riddle suggestes you wouldn't be able to see a computer screen when there is too much radio frequency light around. It makes no sense.
The comments by ankurtg and wmcleod are correct. This teaser is in the Science category but sadly its author has completely misunderstood the science of how noise cancellation works, so the teaser is totally wrong. Too bad.
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