The children under age 5 years have a fully developed inner and middle ears allowing them to hear from 20 Hz to 25,000 Hz. As the age increases, our inner ear changes gradually which cause reduce in hearing capacity from 20 Hz to 20,000 Hz
We can hurt 20 to 20000 hertz but more but all five years old child can hurt more than 25 parts
Oliul answered this
The tympanic membrane which is very thin at early age below five so it can vibrate more in unit time which allow more persistence of hearing ,where as tympanic membrane became thick and rigid which decrease it's vibrating rate to persist sound of high frequency.