A new type of narrow-band wave analyzer is described. This analyzer is different from the conventional analyzers in that the signal frequencies are heterodyned down to a zero beat and passed through low-pass filters rather than being heterodyned to some fixed pass-band which is higher in the frequency spectrum than the components being analyzed.n The general theory of the instrument is described in detail and some of the analyses made with it are presented. Its latent possibilities are discussed for the detection and for the reduction of ships noise. The Operating Instructions and most of the construction details of the latest model are described.
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