Telediffusion De France

Patrice Bourcet

Denis Masse

Jean Pujolle

Alain Komly

Bruno Jahan

Michel Seguin

System for broadcast of data in an audio signal by substitution of

A synchronized broadcast network comprises a main transmitter transmitting an audio source signal to a plurality of receiver/transmitter units remote from each other and from the main transmitter, the receiver/transmitter units broadcasting the audio signal using frequency modulation. In the main transmitter the audio source signal is digitized by sampling it at a predetermined sampling frequency. A digitized signal representing the sampled audio signal is transmitted to the receiver/transmitter units. In each receiver/transmitter unit a reference signal representing the sampling frequency is derived from the received digitized signal and the received digitized signal is passed through a succession of digital processing stages including a stage in which a carrier derived from the reference signal is digitally modulated and a stage in which the result of the digital modulation is digital-to-analog converted. In one of the digital processing stages the received digitized signal is delayed for a predetermined time in order to synchronize the phase of the receiver/transmitter units. All the digital processing stages are synchronized to the reference signal to obtain identical digital modulation of the same carrier for all the receiver/transmitter units. The result of the digital-to-analog conversion stage is transposed to a final frequency derived from the reference signal for broadcasting the analog audio signal using frequency modulation with the same modulation, phase and carrier at all receiver/transmitter units.

Frequency modulation broadcast transmitter synchronization method

Device enabling the direct measurement of the overall insulation level of an acoustic insulation medium with respect to a reference excitation noise signal when said medium is subject to an actual excitation noise signal deviating from the reference excitation noise signal. The device comprises two microphones receiving a first and a second alternating signal respectively representing the noise signal actually transmitted through the medium and the actual excitation noise signal and a read only memory storing spectral components of the reference excitation noise signal in a plurality of given spectral bands. The first and the second alternating signals are decomposed into alternating spectral components in these spectral bands and the alternating spectral components of the second signal are rectified in order to obtain rectified spectral components. These rectified spectral components are added to the alternating spectral components of the first signal relating to the same spectral bands thereby obtaining composite signals each having a direct and an alternating component. These composite signals are selectively passed through attenuators thereby forming attenuated alternating spectral components and attenuated rectified spectral components which are separated from each other. The attenuated rectified spectral components are compared to the spectral components of the reference excitation noise signal relating to the same spectral bands and thereby error signals are obtained respectively corresponding to the spectral bands, and these error signals control the attenuators.

Acoustic insulation measurement apparatus

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Mey, France

Patrice Bourcet