What are those sounds (such as telephone ring tones) that kids can hear but adults cannot?
High frequencies. Almost always, adults lose the sensitivity to high frequencies first. It is not well known how much of this is due to age and how much is due to lifetime exposure to noise, because the two are correlated. Children may hear sounds above 20 kHz, but adults rarely can. In middle or old age, the upper frequency limit gradually descends. You can find out how well you hear different frequencies — including your high frequency limit — on our web service Test your own hearing. In fact, that site may be where some youngsters are downloading their high frequency sounds.
