Abstract: A system for identifying an object, and in particular a vehicle, by analyzing the noise spectrum emitted thereby to determine the basic noise characteristic thereof and then comparing the basic noise spectrum signal with known basic noise spectra. The noise from the object, which includes both the basic noise characteristic and other superimposed noise, is detected and converted to an electrical analog signal which is then sampled. The sampled electrical signal, preferably after passing through an analog to digital converter, is sequentially converted into its orthogonal components in the frequency domain, e.g. by means of a Fourier conversion, converted into a signal with the logarithms of the noise spectrum components, and then reconverted into a signal of the noise spectrum components in the time domain, e.g. an inverse Fourier conversion.