The use of acoustic-emission (AE) techniques integrated with single-particle composite (SPC) mechanical-optical testing is proposed to evaluate and characterize adhesion in particle-filled polymeric composites. It is shown that not only can an intrinsic interfacial strength be determined but also that different types of adhesion mechanisms may be distinguished in terms of straightforward criteria using the wavelet transform (WT) of the acoustic signature, once problems with internal reflections in the test coupon are resolved. The validity of the proposed method is demonstrated with a study of the adhesion of a commercial poly(vinylbutyral) (PVB) to bare and aminosilane-treated glass beads.