Abstract: A spectrum analysis method and apparatus for processing and displaying time series data. The time series data in digital form is decomposed into a plurality of frequency components by means of a set of band pass filters. Adjacent band pass filters have their cut-off frequencies shifted or offset from each other by their passing band widths. Amplitude information of the frequency components may be obtained. For example, the frequency components generated by the band pass filters may be sampled in amplitude at predetermined time intervals. Such sampled amplitudes are then transformed into corresponding densities of a predetermined color including a gray color according to a color (or gray) scale, and displayed on a screen on the basis of a time base of the screen.

Abstract: An electrogastrograph measures an electric signal derived from the stomach's action. The signal is decomposed into its frequency components by means of a plurality of band pass filters, and stored in a storage medium. A method for analyzing data obtained by the electrogastrograph comprises the steps of: decomposing the signal into its frequency components by means of the band pass filters; and, evaluating the stomach in its action on the basis of variations in amplitude of said frequency components.

Abstract: An apparatus for measuring an electrogastrogram and an intestinal electrogram including at least an electrode fixed to a body surface, an amplifier for amplifying a potential detected by said electrode, a low-pass filter for removing frequency signals other than the potentials of the stomach and the bowel amplified by said amplifier and a recorder.The relationship between the frequency of the input signal of said low-pass filter and the phase of the output signal is made linear.