Nrhiav txhawm rau txhawb koj lub qhov chaw ua haujlwm? Peb parabolic flute laum cov khoom yog tsim los coj koj cov khoom lag luam mus rau qib tom ntej. Nrog rau cov cim hluav taws xob tshwj xeeb thiab cov raj nplaim tob, cov tawv no ua kom sai dua li cas tshem tawm thiab txo kom sov, ua rau e ...