moan-sigh theory
A theory developed that shows the moans are the inverse of sighs. Where moans go up then down in tone, sighs go down then up in tone. This theory is useful for people learning Chinese, or taking Mandarin/Cantonese as a Second Language.
According to the moan-sigh theory, the essence of pronunciation for mandarin characters with the 3rd tone is comparable to that of a sigh, or the inverse of a sigh - known as a moan.