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A comment on Hijack - iPhone Sensors Thru Audio Jack. Parent comment

Re:Hijack - iPhone Sensors Thru Audio Jack by acgourley on Saturday February 11, 2012 @01:39PM (#3579798)
It's probably no coincidence it's right out of human hearing range. Most headphone drivers response curve are likely designed to be less efficient at that freq, and thus need more power to create the same loudness. the iPhone's audio driver probably takes this into consideration and drives those frequencies with more power to compensate.

Just a guess, I'm sure they arrived at it purely through trial and error, and were happy to find that it's also a frequency that will be minimally annoying if a headphone happens to be plugged in when the tone is played.

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Re:Hijack - iPhone Sensors Thru Audio Jack by tekromancr on Saturday February 11, 2012 @01:42PM (#3579808)
Minimally annoying my ass. If you are still young enough to hear it it's downright painful!
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Re:Hijack - iPhone Sensors Thru Audio Jack by mkopinsky on Saturday February 11, 2012 @11:13PM (#3581077)
How young is young enough to hear 22 kHz? I am 25 and can barely hear 14kHz. http://www.noiseaddicts.com/2009/03/can-you-hear-this-hearin... In the comments section there people claim to be able to hear 20 and 21, but it seems like not many can hear 22.
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Re:Hijack - iPhone Sensors Thru Audio Jack by marvin on Sunday February 12, 2012 @10:10AM (#3581967)
In practice I'm pretty sure it's more about exposure to loud noises than actual age, and these increase as you age. I know I was able to hear 20kHz at 16, but probably down to 17kHz or so now at 25.

In other words, if you've been to a couple of rock concerts with no earplugs then all bets are off.

Also worth noting that most speakers play 0.5dB below the actual signal at 20000Hz, where anything above that usually isn't specified. So you need specialist audio gear or some measuring equipment to actually try to listen to really high frequencies.

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Re:Hijack - iPhone Sensors Thru Audio Jack by lbotos on Sunday February 12, 2012 @05:41AM (#3581543)
Don't forget with tests like the one that you've linked it depends on your speaker's response to get an accurate reading.
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