Abstract: A data transmission method, particularly in electric networks, in which coded data are blockwise modulated onto several carrier frequencies within one or several particular frequency bands by an orthogonal frequency division multiplex method (OFDM) and in which the signal corresponding to a data block and obtained by inverse Fourier transformation is transferred to a receiver for a predetermined time duration (T), where individual signals succeed as signal blocks in time. In some embodiments, each signal is multiplied with a window function before transmission, the absolute value of the Fourier transform of which has a zero crossing at the respectively used carrier frequencies, and has secondary maxima, which have a damping of at least −30 dB in relation to the main maximum. In some embodiments, a digital filter can be used instead of the window function, the digital filter having an odd number of coefficients Ck, k=−m, . . . 0, . . .

Abstract: A sound pick-up and reproduction system includes at least two sound sensors, such as microphones, situated at different distances from a sound reproduction device, such as a loudspeaker. A processor responds to amplitudes and phases of signals outputted by the at least two sound sensors to control a signal outputted to an amplifier and adapted to drive the sound reproduction device, thereby reducing echoes in the sound reproduction device output caused by acoustic coupling between the at least two sound sensors and the sound reproduction device.