Ultrasound refers to a sound wave with a frequency greater than the upper limit of human hearing, which is generally over 20 kHz. In general, humans can hear sounds with a frequency between 20 Hz and 20 kHz.
A tribe can be defined as an aggregate of people linked together by means of social ties, a common language and the recognition of a common cultural heritage. Amerinds – The term is applied to the people of mixed European and American Indian blood in North America.
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