Defect dynamics in copper single crystals is investigated using a modern acoustic emission technique including analysis of the shape and power spectra of individual pulses. Crystals with various tensile orientations providing different dislocation behaviors such as single and multiple glide, formation of cells and Lomer-Cottrell locks, etc., are examined. Features of AE corresponding to stages I, II and III of plastic deformation are discussed in terms of statistical treatment of spectral parameters. It is shown that the AE spectra are sensitive to the transitions of deformation stages. The results of AE analysis are discussed from the viewpoint of relationships between dislocation emergence to a free surface and dislocation breaking away from pinning points.