During puberty, sounds differ between  males and females.This is Because of the Adam's Apple.In Males this Adam's Apple grows larger which makes their sound harsh and Loud. Similarly in Females this Adam's Apple help them to have more pitched and Sweet Voice.
That is why females sound is Different from a Male Voice,due to this Reason.

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arnav girls don't have adam's apple
they have
yes u r right they but as it not well grown to give harsh n rough voice
as said in the second answer
Because males have adam's apple which gives hard voice to males whereas girls have adam's apple but it is not well grown to give hard voice. Hence girls voice is different from males voice.

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