Answer:
frequency
Explanation:
The frequency of the voice can tell a lot about the age of the speaker, even if we don't see them.
Children tend to have a very high frequency of the voice - it is what we hear as children's high pitched or squeaky voice, which helps us distinguish it is them.
Men's voices, when they speak normally, go up to 155Hz, women's up to 255Hz, but children's voices are raging between 250 Hz to 300Hz, or even higher.
In most cases, children will have a higher frequency of the voice than any full-grown adult.
It is also noted that even older people, as they age, have notable changes in voice. Adult men that usually have low voice frequency tend to have a higher and higher frequency of the voice as they age. Women go through a different process - they have a high frequency of the voice and during the aging process, it lowers down notably according to studies.
