Cov yam ntxwv ntawm lub vijtsam zaub sawv ntsug xav tau tias hauv qab xav tau kev txhawb nqa, thiab nws yog qhov haum rau cov khoom me ntawm cov khoom me me kom muab tso rau hauv txee thiab txheeb xyuas cov rooj. Cov khoom siv feem ntau siv duab zaub muag zaub yog ib qho zaub ib leeg, uas tau muab faib ua cov kauj ruam, baffle, nuv, thiab lub qhov raws nws cov qauv sab hauv.