This is an mp3 of that high-frequency tone that people over 30 generally have a hard time hearing. British shop keepers are credited for leveraging the phenomenon by blasting the sound over loudspeakers mounted outside their stores to deter loitering street urchins.
It wasn’t long before inventive students began using the sound as a ringtone in the classroom to signal incoming text messages without alerting the teacher.
Very clever monkeys indeed.
Entries (RSS)