Origins of the Domino Theory. In September 1945, the Vietnamese nationalist leader Ho Chi Minh proclaimed Vietnamâs independence from France, beginning a war that pitted Hoâs communist-led Viet Minh regime in Hanoi (North Vietnam) against a French-backed regime in Saigon (South Vietnam).
The human range is commonly given as 20 to 20,000 Hz, though there is considerable variation between individuals, especially at high frequencies, and a gradual loss of sensitivity to higher frequencies with age is considered normal.
The human voice and the human ear are a precisely tuned set of instruments. Theoretically, the human ear can hear from 20 hertz (Hz) to 20,000 Hz, but is most sensitive in the range of 300 Hz and 3000 Hz; a person with normal hearing should be able to distinguish more than 250,000 separate sounds.