A high-speed camera was used to record the motion of a fiber below both a melt-blowing slot die and a melt-blowing swirl die. These recorded images were processed to determine the frequency and amplitude of fiber motion during melt blowing. The operating variables investigated included polymer flow rate, air flow rate, polymer temperature, and air temperature. A crossover counting method was developed to determine the frequency of fiber motion. The frequencies determined from this counting method favorably compared with frequencies determined by taking fast Fourier transforms of the fiber displacement data. Experimental results for frequency and amplitude were compared to predictions from a three-dimensional mathematical model for the melt-blowing process.