13 June 2006
Can you hear me now?
A kid's dream come true: a cell-phone ringtone that grownups can't hear, so you can take that important call in English class without tipping off the teacher.
The argument is persuasive:
While most human communication takes place in a frequency range between 200 and 8,000 hertz (a hertz being the scientific unit of frequency equal to one cycle per second), most adults' ability to hear frequencies higher than that begins to deteriorate in early middle age.
Indeed. Just ask Pete Townshend.
Since the Times was kind enough to provide a sample of the 17-kHz tone (scroll down on the left side of the article, or use this link to the MP3 file), I figured the least I could do, as an old man who has spent most of his life with the headphones cranked up to near-Spinal Tap levels, was to make sure that I wouldn't be hearing this thing next time I hit the mall. With the expectation of finding some small amount of residual hearing in these old ears, I spun the volume knob over to the right ...
... and just as quickly spun it back, my ears ringing.
This demanded an investigation, so I loaded the proffered file into Audacity and got this:
How to explain this? For one thing, my listening post is rather a lot quieter than your average classroom; for another, while the center frequency is indeed around 17 kHz, there is substantial acoustical energy well below 17 kHz, and that's probably what I'm hearing, even though it's 40, even 50 dB below the peak level. (That peak near 25.5 kHz is likely some sort of distortion product.) And at "normal" sound levels, for this purpose defined as "where I normally run my sound card and speakers," it's pretty close to inaudible; running the air conditioner is more than enough to drown it out.
Still: don't they use vibrate anymore?
(Via Tinkerty Tonk.)Posted at 12:42 PM to Say What?