Propeller Head Plaza

Technical and scientific discussion of amps, cables and other topics.

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Re: Human hearing

Posted by jk on November 12, 2002 at 09:56:37:
This topic has always been close to my heart. I'll never forget the time when at the age of about 12, I was in the Smithsonian and they had the moon rocks (circa 1972) on display. I could hear the burglar alarm (it was more painful than anything else) as you got close to it, no one else could hear it. It was an sound so high pitched I can't even describe it. I'm 43 now, doubt I can hear anything like that - I wish two things: 1) I had measured how high I could hear back then (burgular alarms, dog whistles, TV's) 2) I hadn't listened to such loud music at times over the years. (I remember how proud I was that my ears rang for 2 days straight after seeing some stupid band - oh well we all get smarter)
I can still hear dog whistles, what frequency do you think that would typically be at? BTW - I wouldn't describe it as a pleasant tone, it is bordering on painful. I met with a gentleman who had his MD and specialized in the ear. He wouldn't buy it, he explained to me that the mechanics of the human ear make it literally impossible to vibrate (and therefore hear) at frequencies much above 20K HZ. On the other hand, I saw an interesting show on ultrasonic experiments. The scientists verified that a 30Khz signal was present at the transducer by mechanically coupling their teeth/jaw to the transducer - they just used a rod of wood (or metal? I forget). They placed the rod on the transducer, then bent down and put their tooth on the end of the rod. When the skull vibrated it was perceived as sound. Interesting isn't it?