I'm not the first to write about the high-pitched ringtones that youngsters are downloading onto their phones. The ringtones are of an extremely high frequency "which often exceeds the hearing range of adult teachers."
In my experience, many schoolkids don't even try to conceal what teachers call "off-task" behaviour". During my brief spell as a secondary school science teacher, a minority of my pupils spent the whole duration of every one of my lessons either sending text messages to friends or listening to music on their iPods.
Anyway, I realized that old people could not hear high-pitched sounds when I was about 10 years old. The photocopier in my father's upstairs study would emit a high-pitched sound when left unused for a few minutes. I knew when parents had left the machine switched on because I could hear the sound from the bottom of the stairs.
"You've left the photocopier on again," I'd often say to them. When asked how I could tell, I'd mention the sound, which I quickly realized they couldn't hear. Based on these observations, I deduced that old people couldn't hear high-pitched sounds. Ten years later, I found that my theory was correct, and learnt the scientific basis of it in cellular neurophysiology lectures.A healthy young adult can perceive sound frequencies from about 20 Hertz (Hz, or cycles per second) to 20 kiloHertz (kHz). Sound waves are transduced into electrical impulses by the hair cells in an inner ear structure called the cochlea. These signals are then relayed to the auditory cortex via the auditory nerve.
The arrangement of hair cells in the cochlea is much the same as that of keys on a piano, with cells responding to high frequency noises at one end and cells responding to low frequencies at the other. With age, there is a progressive degeneration of hair cells, which starts with cells that perceive the highest frequencies, and begins at around middle-age.