June 22, 2006

Now you hear it...

NPR and The New York Times have recently noted the appearance of a high-pitched 'adult-proof' cellphone ring tone. The idea is that kids would employ this ring tone to indicate that a text-message has arrived, in situations like high-school classes where text-messaging is frowned-upon. Since the ability to hear high-frequency sounds declines with age, the teachers can't hear the ring tones. Or so the story goes.

Of course, being 43, an age where one is just becoming a tad defensive about any signs of such age-related deficits, I lost no time in downloading the NPR ring tone mp3 and you will all be happy to know that (for now) I can hear it just fine.

The ring tone at the NPR site is a relatively pure tone at 15 kHz (that's 15 kilohertz, which is pretty darn high). The ability to hear of course depends on how loud the sound is; this ring tone was at 85 dB. Sure enough, the audiology literature (Sakamoto et al 1998) suggests that your average 40-49 year old can hear 15 kHz just fine. The threshold of audibility for people of my generation (or anyhow my decade) for a 15 kHz signal is, on average, 90dB, plus or minus about 10 dB.

Now I gather that the ring tone was an offshoot of an earlier product, the Mosquito, a loud pulsed high-frequency sound designed to keep teenagers from loitering around convenience stores. NPR reported that sound as being at 17 kHz. 17 kHz is REALLY high. Sakamoto et al. show that the average 10-19 year old can hear 17 kHz at 80 dB. I can hear 17 kHz, barely, at 90 dB or more. Sakamoto et al suggest that the average person in my decade can only hear 17 kHz if it is as loud as 120 dB or so, which suggests that playing the drums can't be as bad for one's hearing as my parents thought.

Anyhow, this particular issue with technology has not yet arisen in my classroom, although like most college professors these days I do find myself challenged to keep the undergraduates paying attention instead of reading their email. One more thing to keep us on our toes.

Posted by Dan Jurafsky at June 22, 2006 03:25 AM