Abstract: An electronic board for cooperation with a computer and a group of noise measuring instruments, for displaying side by side noise curves for various gear pairs of a gearbox for differing frequencies selected by filter means (15,21,20,17,19,18,23) in an audio frequency band, to which the human ear is sensitive. A frequency sensitive Fourier analysis is conducted continually at chosen rpm steps spaced over the desired range, in order to produce the curves. Noise inherent in a design of transmission, or only present in isolated samples thereof thereby denoting wear or other defect or damage, can thus be investigated, analyzed and possible remedies applied.