Acoustic emission technique has many advantages because it is noninvasive and relatively inexpensive.A set of apparatus was built to measure the velocity of different-sized glass beads impacting upon a steel plate and the arising acoustic emission signal by use of a broadband piezoelectric transducer simultaneously.The impact velocity was measured by optical cross correlation velocimetry.The Welch method was used to analyze the characteristics of power spectrum of acoustic emission signal.Power spectrum mainly focused on the frequency band of 50—400 kHz and its peak moved to the lower frequency band as the particle size of glass beads was larger.Based on the Hertz-Zener theory and analytical approximation of acoustic emission spectrum

a least squares method was used in the frequency domain with the goal of calculating particle size from the experimental data.The results of the glass beads with diameters over the range of 300—400 μm and 400—600 μm agreed well with the respective results of sizing by CAMSIZER.It also provided a new way to measure particle size distribution.