To fully understand particle interactions with both substrate and neighboring particles in Cold Spray (CS), ultrasonic monitoring and acoustic emission of particle agglomerate impact were studied. The results obtained show the influence of particle agglomeration density on stress and strain distribution in the particles and at the particle interfaces. The results are compared with metallographic structures of real coatings. The development of monitoring procedure is made using acoustic methods, specifically testing during the actual spray process itself. It is shown that the final thickness as well as the dynamics of buildup can be evaluated. Cross sections of the coating thickness are also easy to obtain and show true profiles of the coating. Comparisons of real thickness and acoustically estimated thickness show a close linear relationship.