Let's assume that there is a signal $f(t)$, $0\le t \le T$. Then, is there any special meaning of the signal $g(t) =f(t) \times \sin(\omega t)$? Like AM transmission. What is shown/heard when we play $g(t)$ in an audio player? Is there/what are meaningful differences between $g(t)$ and $f(t)$?