Tonight, thanks to NPR, i got some more information about the supposed anti-adult ringtone.
For those unfamiliar with this story, In Britain an enterprising gentleman has determined that the best way to deter local yoots from hanging around the front of the drugstore is by playing a very high pitched tone at them. The theory being, those yoots who's hearing has not yet been destroyed by their iPods or curb thumping bass beats would find the tone so annoying they'd leave. It is, by most reports, a success.
Some even more enterprising young yoots, have determined that this magical tone is useful for their own evil purposes because reportedly most adults over the age of 30 are not able to hear it.
Mind you, i can hear a CRT refresh scan rate. In fact, my hearing tops out at around 16,125Hz (give or take a dozen or so Hz). i was the one that told my parents the electronic mosquito repeller batteries were dead. So, naturally, i was very interested in hearing this inaudible tone.
So i clicked on the link, and heard nothing. Odd.
So i turned up the volume. Still nothing. i tried playing a different noise just to see if my speakers were working and once my ears stopped ringing, i tried it again (Note to past self: Turn down sound BEFORE playing test sound.) Then i turned on the "Bars" Visualizer. That's the el-cheapo oscilliscope on your computer that tells you what frequencies are being played. Still nothing.
Ah-HA!
See, even very high pitched sound has to show up on those. You should see something like this:
My bet? Since most audio compressors (like RealAudio, WMV, and MP3) toss out very high and very low frequencies in order to save bandwidth, the baby got tossed out with the bathwater. As an added benefit, since the tone is reported to be inaudible to anyone over the age of 30, the person doing the proof probably didn't hear the tone before they encoded it either.
Oh, and by the way? Most cellphone speakers aren't capable of playing that high a frequency either, so the tone usually gets cranked down to the 16K range. Bingo, you're in my territory. i'll also add that a number of computer speakers also can't manage that range
And just in case you all want to find out how good your hearing is (or just want to drive the neighbor's dog nuts), here's a 2 second burst of 20KHz, the maximum human audible tone. Anne Marie hears it just fine.
The BBC has more along with a working sound file with background noise included. Boing Boing also has some discussion on the cell phone part.
I could just barely hear the 20KHz one (I'm sixteen) but my dog didn't respond at all (not that I left it playing that long, it's pretty annoying)
Ah, Thanks Caleb!
Yeah, I don't have a scope right now (I'm travelling, more about that later), but that's definitely hovering between 15K and 16K. It's less than I thought.
Reminds me of a mosquito repeller a Target Store had when I lived back in Virginia. It was cranked up pretty high and I got a splitting headache just walking up to the place.
People used to look at me funny when I stuck my fingers in my ears whenever I walked up to the door.
As for the 20KHz, dang, you all have definitely got better high pitch hearing than I do.
Having heard my fair share of test tones during my audio days, I was a little surprised to hear nothing at 16kHz. Well, nothing but the crappy noise floor of my computer gear. Ugh.
I'm sure it was caution on JR's part, but the 16kHz tone is -12dB down. Adjust volume and try again, there it is. And barely, just ever so barely I can hear the 20kHz.
On some of my computers all you can hear is the sound "card" noise floor and the switching on and off as it comes out of low-power mode and then goes back to sleep.
My cell phone will audibly play the 16kHz tone, but the sound of the amp switching on and off is louder (to me). If I were a punk-ass kid, and people actually called me I'd just use the vibrate feature on the phone.
I'm guessing that this is a story that someone invented for the media, like 'toothing.
I figured if adults weren't hearing the phones ring, and speaker phones can't produce tones normal people can't hear. Then it had actually been invented by some clever teens in order to dupe their superiors into thinking they had been outsmarted. Which I find incredibly clever. Tricking people into believing they've been tricked.
I am 53 years old and I can hear it.
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I can hear it.