Abstract: The invention relates to a programmable fast Fourier-analyzer device realized with MOS microprocessors, suitable for carrying out tasks connected with measurement, control and control engineering such as sound and vibration analysis. The frequency analyzer according to the invention contains an A/D converter, a plurality of microprocessors each, complete with a memory unit, for measurement data acquisition, calculation of the FFT and control of a cathode-ray display. Data transfer between the microprocessors is realized by repeated exchange of read and write memories between the microprocessors. The control element of the apparatus is an alphanumeric keyboard enabling the analyzer to be programmed in known program languages.

Abstract: The subject matter of the invention is a directional electro-acoustical converter, primarily a cardioid sound radiator which, in spite of its small dimensions, has cardioid directivity diagram and at the same time wide transmission band.The known solutions of the cardioid sound radiator have frequency responses falling towards the low frequencies thus being generally suitable for the transmission of speech informations. On the contrary, the directional converter according to the invention provides for a wide transmission band in the loudspeaker operating method being thus suitable for the transmission of musical programs, too. To the membrane of the converter according to the invention at least two phase shifting members having different sound route distances are coupled by means of acoustic coupling elements.

Abstract: Singing suppressor device for preventing singing or self-oscillation caused by acoustic feedback arising in an audio-frequency signal transmitting electroacoustic chain comprising a sound sensing device (microphone), an amplifier and a sound generator. The invention relies on the variation in the temporal order of the delay time of an electrical delay unit, on an analog and/or digital principle, inserted into the electroacoustic chain. The variation of the delay time is performed by a control generator which, with the aid of an appropriate circuit (e.g. a modulator or an auxiliary generator) continuously changes the delay time as a function of time. This ensures that singing arises only at a considerably higher sound pressure level, because owing to the varying delay time appropriate amplitude, frequency and phase conditions to induce feedback are met for a short time or moment only.