The ear has a set of filaments to vibrate in resonance with incoming sound-waves.耳朵里有一组细丝能和进入的声波产生共振。When the electric current is turned on, it ignites the tungsten filaments in the bulb.电流一接通就使灯泡内的钨丝灼热发光。Toothbrushes should be replaced when the filaments become worn.牙刷毛磨损后就应该更换了。