Abstract: A method for the quality control of processes and construction components by diagnosing their sound vibrations during a predetermined period of time. The invention has the purpose of objectively and reliably evaluating acoustic vibrations, independent of the subjective evaluation of monitoring personnel, which can also detect very fine differences in the vibration behavior of the monitored device at an early time. To this end, the invention provides two possible solutions. In one method according to the invention, the oscillation height (.DELTA.A.sub.1 . . . .DELTA.A.sub.n) of the amplitudes of the signals are measured, depending upon a predetermined discharge time of an integrator (FIG. 1). In a second method, the impulse density of those impulses of the signal which exceed a predetermined threshold value (S) are measured.

Abstract: A method of non-destructively testing construction elements accessible from only one side by measuring their resonant oscillations to detect flaws in them without scanning. A test piece (1) is excited with a narrow band ultrasonic oscillation whose frequency is varied; the amplitudes of the resonant oscillations are measured and plotted in an xy coordinate system against the frequency of the exciting ultrasonic oscillations.