Acoustical radiation is generated and applied to the bonding interface between a radiation transmission material and a radiation attenuating material to determine adhesion quality by extraction of data from a response signal produced by echoes reflected from both the interface and the radiation entry surface on the radiation transmissive material exposed to the generated acoustical radiation. Signal phase cancellation between the echoes from the entry surface and bonding interface produce a signal signature from which the quality of bonding is evaluated. By partial attenuation of the echo from the entry surface, the signature is maximized.